Surface treating apparatus and method

ABSTRACT

A back-up apparatus for use with a surface treating apparatus can include a back-up plate having a pad attachment face and a back-up pad having a first pad face and a second pad face. The back-up apparatus can also include a porous interface layer. The interface layer can include an outer face. The back-up apparatus can also include a layer of a first adhesive on the outer face and extending into the interface layer, and a layer of a second adhesive provided on the layer of the first adhesive. The second adhesive can be selected to releasably adhesively bond to an abrasive sheet. The first and second adhesives can be selected such that the adhesive bond between the first adhesive and the second adhesive is stronger than the adhesive bond between the second adhesive and the abrasive sheet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 13/395,353, filed Apr. 13, 2013, which is a national phaseentry of PCT/CA2011/000910, filed Aug. 9, 2011, which claims priority toPCT/IB2010/001988 filed Aug. 10, 2010, each of those applications beingincorporated herein in their entirety by reference.

FIELD

The present subject matter relates generally to apparatus for treating asurface, for example by sanding, grinding, polishing and the like andmethods for treating a surface by, for example, sanding, grinding,polishing, buffing and the like.

BACKGROUND

PCT publication WO99/24222 (Luedeke) discloses a backup pad for engagingand supporting abrasive sheets, the backup pad is mounted securely to adrive shaft to prevent relative rotation thereto, and to allow easymounting and dismounting of the backup pad to the mounting shaft withoutthe use of tools. The backup pad includes a body comprising a frontsurface and a back surface, releasable engagement means provided on thefront surface for releasably engaging an abrasive article, and amounting boss provided on the rear surface. The mounting boss includes afirst end facing away from the body, and an opening in the first end ofthe boss, the opening being formed by an inner surface generallyperpendicular to the body and defining a non-circular cross section. Theopening includes elastic means such as an o-ring for releasably engaginga drive shaft mounted in said opening.

U.S. Pat. No. 4,558,542 (Marton) discloses an abrasive or sanding discfor use on a rotary or double action backup pad. The abrasive discincludes on its rear surface a smooth flexible coating to give strengthto the sandpaper and to stick to a feathering adhesive on a backup pad.The smooth coating is typically a nylon coating or an adhesive whichbonds to the back of the sandpaper and acts as a coating. The coatingalso adheres strongly to a feathering adhesive on a backup pad. Thesanding disc can be strongly secured to the backup pad but can be pulledaway from it, leaving the feathering adhesive on the backup pad.

U.S. Pat. No. 2,286,208 (Kirchner) discloses providing a layer ofpressure sensitive adhesive on either the back of an abrasive coatedsheet or on a permanent backing, by means of which the abrasive coatedsheet can be quickly and easily attached to the permanent backing andheld in firm attachment thereto during working operation, but which maybe readily detached therefrom when the abrasive coated sheet becomesunduly worn or unfit for further service.

SUMMARY

This summary is intended to introduce the reader to the more detaileddescription that follows and not to limit or define any claimed or asyet unclaimed invention. One or more inventions may reside in anycombination or sub-combination of the elements or process stepsdisclosed in any part of this document including its claims and figures.

A surface treating apparatus can include a driving apparatus and aback-up apparatus. The back-up apparatus can include a rear face (facingthe driving apparatus) and an opposed abrasive mounting face. A suitableabrasive sheet can be releasably attachable to the abrasive mountingface. The releasable engagement between the abrasive sheet and theabrasive mounting face may help facilitate the replacement of a used orworn abrasive sheet with a new, replacement abrasive sheet or anabrasive sheet with a different grit. The driving apparatus can be anysuitable type of driving apparatus that is compatible with the back-upapparatus, including, for example a rotary driving apparatus (including,for example electric and air-powered rotary drivers and grinders), and adouble action driving apparatus.

In accordance with one aspect of the invention, the abrasive sheet canbe attached to the abrasive mounting face using a releasable, reusableadhesive. Providing a releasable, reusable adhesive may help facilitatereplacement of worn abrasive sheets. In accordance with this aspect theback-up apparatus can include a back-up plate, a back-up pad and anadhesive interface layer provided on the back-up pad. The back-up padcan provide mounting support for the abrasive sheet and, preferably,provides a cushioned backing. During use, an abrasive sheet is subjectedto substantial forces in the plane of the abrasive sheet. If theadhesive used to secure the abrasive sheet in place is too weak, thenthe sheet may become dislodged during use and this may mar or otherwisespoil the surface being treated. If the adhesive is too strong, it maybe difficult to remove worn abrasive sheets from the back-up pad, and/orportions of the abrasive sheet may tear and remain fixed to the back-uppad. An advantage of the interface layer is that it may provide astronger, releasable attachment of the abrasive sheet to the back-uppad.

The abrasive sheet can include a back face that is compatible with theadhesive on the interface layer. Preferably, the back face is providedby a film layer that is bonded to the abrasive sheet. The film layer canbe stronger than the abrasive sheet, and can help strengthen theabrasive sheet during use, and help reduce tearing or ripping of theabrasive sheet when it is peeled off of the adhesive interface layer.This may help prevent small pieces of the abrasive sheet from remainingdeposited on the back-up apparatus, which may interfere with placementof the replacement abrasive sheet.

Preferably, the interface layer includes a plurality of upstandingfibres that are coated with a base adhesive. The base adhesive can thenbe covered with a second, tacky adhesive, that can be releasably bondedto the abrasive sheet. The adhesives can be selected so that the bondbetween the base and tacky adhesives is stronger than the bond betweenthe tacky adhesive and the abrasive sheet. This may allow the abrasivesheet to be separated from the interface layer, without transferring thetacky adhesive from the interface layer to the abrasive sheet.

In accordance with this aspect, a back-up apparatus for use with asurface treating apparatus can include a back-up plate having a padattachment face, a back-up pad having a first pad face, secured to thepad attachment face, and an opposed second pad face. The back-upapparatus can also include a porous interface layer. The interface layercan include an inner face, secured to the second pad face, and an outerface. The back-up apparatus can also include a layer of a first adhesiveon the outer face and extending into the interface layer, and a layer ofa second adhesive provided on the layer of the first adhesive. Thesecond adhesive can be selected to releasably adhesively bond to anabrasive sheet. The first and second adhesives can be selected such thatthe adhesive bond between the first adhesive and the second adhesive isstronger than the adhesive bond between the second adhesive and theabrasive sheet whereby the layer of second adhesive remains bonded tothe layer of first adhesive when the abrasive sheet is separated fromthe back-up apparatus.

The back-up pad can resiliently flexible and the interface layer isflexible whereby the back-up pad flexes to follow the contours of asurface being sanded.

The interface layer can be a pile material and the outer face caninclude a plurality of engagement fibres extending away from theinterface layer.

The first adhesive can be mechanically worked into the interface layerand can extend below the outer face to provide a three dimensionaladhesive layer.

The interface layer can cover substantially all of the outer face.

The surface area of the interface layer can be greater than the surfacearea of the pad mounting face of the back-up plate.

The back-up pad can be a natural or synthetic rubber.

The bond between the second adhesive and the abrasive sheet can have afirst bond strength at 25° C. and a second bond strength at 400° C. Thesecond bond strength can be at least 80% of the first bond strength.

The back-up plate can include a plurality of plate suction aperturesfluidly connectable to a suction housing. The back-up pad can alsoinclude a plurality of pad suction apertures in fluid communication withthe plurality of plate suction apertures and the interface layer caninclude a plurality of interface suction apertures in registration withthe pad suction apertures.

The back-up plate can include a plurality of plate suction aperturesfluidly connectable to a suction housing, the back-up pad comprises anopen pad suction channel in fluid communication with the plurality ofplate suction apertures and opening to the second pad face and theinterface layer comprises an interface suction opening registered withthe pad suction channel.

Also in accordance with this aspect, a method of replacing an abrasivesheet on a back-up apparatus can include the step of providing a back-upapparatus having, a back-up plate having a pad attachment face and aback-up pad. The back-up pad can have a first pad face secured to thepad attachment face, and an opposed second pad face. The back-upapparatus can also include a porous interface layer having an inner facesecured to the second pad face, and an opposed outer face. The back-upapparatus can also include a layer of a first adhesive covering theouter face and coating a plurality of discrete fibres extending awayfrom the abrasive mounting face, and a layer of a second adhesiveprovided on the first adhesive and releasably adhesively bonded to theabrasive sheet. The method can also include the steps of separating theabrasive sheet from the interface layer; providing a replacementabrasive sheet comprising a first side covered with abrasive materialand an opposed second side configured to releasably engage the layer ofsecond adhesive; aligning the second side of the replacement abrasivesheet with the abrasive mounting face of the interface layer; andpressing the second side of the replacement abrasive sheet against thelayer of second adhesive on the interface layer.

The abrasive sheet can include a base layer. The base layer can providethe first side covered with abrasive material, and can include anopposed rear face. The abrasive sheet can also include a film layerbonded to the opposed rear face of the base layer. The film layer caninclude the opposed second side configured to releasably engage thelayer of second adhesive.

The step b) may be completed in the absence of transferring the secondadhesive from the abrasive mounting face to the abrasive sheet.

The method can also include sealing the peripheral edges of the filmlayer to the abrasive mounting face whereby debris is inhibited frombeing deposited between the abrasive mounting sheet and the film layer.

The film layer can be mylar.

The back-up pad can be resiliently flexible and the interface layer isalso flexible whereby the interface layer flexes with the back-up pad

In accordance with another aspect of the invention, which may be used byitself or with any one or more other aspects of the invention, theback-up apparatus can have an open sided channel in the outer facethereof, the open sided channel is configured to connect a plurality ofsuction openings in an abrasive sheet in fluid communication with asource of suction. For example, the open sided channel may overlie atleast two suction openings in an abrasive sheet and, preferably, mayoverlie all of the suction openings in an abrasive sheet. Accordingly,the rotational alignment of the abrasive sheet during the mounting ofthe abrasive sheet to the back-up pad may be simplified and optionallymay be eliminated.

Optionally, a surface treating apparatus can be configured to include asuction system. The suction system can be operable to extract dust andother particulate matter from the region between the abrasive sheet andthe surface being sanded. Removing debris from the surface using thesuction system may help inhibit clogging or fouling of the abrasivesheet, and may help improve sanding performance.

Providing an open suction channel may eliminate the need forrotationally aligning the abrasive sheet with the back-up pad whenplacing the sheet on the pad. It may also help balance the suctionapplied to the plurality of suction holes in the abrasive sheet.

In accordance with this aspect, a back-up apparatus can include aback-up plate having a pad attachment face, an opposed rear face and atleast one plate suction aperture extending through the back-up plate.The back-up apparatus can also include a back-up pad having a first padface provided on the pad attachment face, and second pad face forsupporting an abrasive sheet. A suction channel can be formed in theback-up pad, and can be in fluid communication with the at least oneplate suction aperture. The suction channel can be registrable with aplurality of discrete suction apertures in an abrasive sheet.

The back-up apparatus can also include an interface layer comprising aninner face, fixedly fastened to the second pad face, and an opposedabrasive mounting face. The interface layer can include an interfacesuction opening registered with the open suction channel.

The suction channel can include a channel endwall disposedlongitudinally between the second pad face and the first pad face, afirst channel sidewall extending from the channel endwall to a firstchannel edge on the second pad face and an opposed second channelsidewall extending from the channel endwall to a second channel edge onthe second pad face.

The first and second channel edges can be separated by a channel width,that is equal to or greater than an aperture width of the plurality ofplurality of plate apertures. Optionally, the channel width can bebetween about 5 and about 15% of the diameter of the back-up pad.

The channel endwall can be positioned intermediate the abrasive mountingface and the first pad face.

The suction channel can extend through the back-up pad, from the secondpad face to the first pad face and the channel endwall can include aportion of the pad attachment face of the back-up plate.

The suction channel can be generally circular as viewed from theabrasive mounting face and can be a continuous channel.

The back-up apparatus can include a central axis and the first andsecond channel edges can be concentric and centered about the centralaxis.

The suction channel can be generally U-shaped and can open toward thesecond pad face.

The back-up pad can be formed from a resiliently flexible material andcan flex to follow surface contours of a surface being sanded.

The suction channel can have an open side on the second pad face thatextends along the second pad face so as to be registerable with at leasttwo of the suction apertures in the abrasive sheet.

In accordance with another aspect of the invention, which may be used byitself or with any one or more other aspects of the invention, a surfacetreating apparatus can include a suction apparatus that is spaced apartfrom the back-up apparatus be a suction spacing distance, and thesuction spacing distance can be adjustable. Adjusting the suctionspacing distance can help regulate the amount of suction applied via theback-up apparatus. Varying the amount of suction that reaches thesurface being treated may be desirable. If the applied suction is toostrong, the back-up apparatus may become non-rotatably stuck to thesurface being treated. This may inhibit the surface treating operationand may mar or otherwise damage the surface. If the applied suction istoo weak, it may be ineffective at capturing dust and debris generatedby the surface treating process.

Optionally, the suction spacing distance can be configured to encourageat least some suction air flow to enter the suction housing via the gapbetween the housing and the back-up plate. In this configuration, thesuction apparatus may be able to capture dust and debris escaping fromthe perimeter of the back-up apparatus, and draw the debris into thesuction housing. This type of suction can be used in combination withthe suction passages that extend through the back-up apparatus.

Optionally, the surface treating apparatus can include one or morespacer elements that can be positioned between the back-up plate and thedriving apparatus. By varying the number of spacer elements used, thedistance between the back-up plate and the driving apparatus can bemodified. If the suction housing is mounted on the driving apparatus,changing the distance between the back-up plate and the drivingapparatus also changes the distance between the back-up plate and thefirst edge.

Alternatively, or in addition, the suction apparatus can be adjustablesuch that an edge of the suction apparatus is moveable relative to thedriving apparatus, and the back-up apparatus. Moving the edge of thesuction apparatus closer or farther from the back-up apparatus maydecrease or increase the suction spacing distance, respectively, whichmay increase or decrease, respectively, the amount of suction.

In accordance with yet another aspect of the invention, which may beused by itself or with any one or more other aspects of the invention, aback-up apparatus can be provided with one or more internal air suctionconduits configured to connect at least one suction opening in anabrasive sheet in fluid communication with a source of suction, forexample the suction apparatus. The internal suction conduits can extendthrough the interior of the back-up apparatus, and can connect suctionapertures in the outer face of the back-up pad with suction apertures inthe back-up plate. Optionally, the apertures in the outer face back-uppad can be radially outboard of the suction apertures in the back-upplate and the internal suction conduits can extend therebetween in agenerally radial direction. If the back-up apparatus is used in rotaryapplications, for example grinding, it can be desirable to position theback-up pad suction apertures toward the edge of the back-up pad. Thisconfiguration may help capture dust and debris that is directed towardthe edge of the spinning back-up apparatus.

In a particularly preferred embodiment, an internal channel can beutilized in combination with one or more open channels. Providinginternal suction conduits may facilitate suction of debris through theback-up apparatus.

In some instances, it may be desirable to use a common suction apparatusin combination with multiple, differently sized and/or configuredback-up apparatuses. In such instances, it may be desirable to configurethe back-up apparatuses to have their suction outlets (e.g. platesuction apertures) in a generally similar, or generally the sameconfiguration that is compatible with the configuration of the suctionapparatus inlet. Internal suction conduits that extend in the generallyradial direction may be used to fluidly connect a variety of differentlysized and positioned back-up pad suction apertures (for exampleapertures that are radially outboard the sidewalls of the suctionhousing) to plate suction apertures that are positioned in a desired,standardized configuration (for example radially inboard of the suctionhousing sidewall).

Optionally, the back-up apparatus can also include an internal suctionplenum that is in airflow communication with some or all of the internalsuction conduits. The suction plenum can also be in air flowcommunication with the back-up pad suction apertures and back-up platesuction apertures. Providing a suction plenum may help equalize thesuction in each of the internal conduits.

In accordance with at least some of these aspects, a back-up apparatuscan include a back-up plate having a pad attachment face and alongitudinally opposed rear face. The back-up plate can include acentral axis and a plate suction aperture extending through the back-upplate. The back-up apparatus can also include a back-up pad, having afirst pad face, provided on the pad attachment face and a second padface for supporting an abrasive sheet. The back-up pad can include a padsuction inlet in the second pad face. The back-up apparatus can alsoinclude an internal suction conduit extending transversely through theback-up pad and connecting the pad suction inlet with the plate suctionaperture.

The plate suction aperture an be radially spaced apart from the centralaxis by a first radial distance and the suction inlet can be radiallyspaced apart from the central axis by a second radial distance. Thesecond radial distance can be greater than the first radial distance.The internal suction conduit can include an upstream end in fluidcommunication with the suction inlet and a downstream end incommunication with the plate suction aperture for communication ofsanding waste through the back-up apparatus. The internal suctionconduit can be positioned longitudinally intermediate the first andsecond pad faces.

The back-up apparatus can also include an interface layer comprising aninner face, fixedly fastened to the second pad face, and an opposedabrasive mounting face, the interface layer can have an interfacesuction aperture registered with the suction inlet in the second padface.

The internal suction conduit can include a first end wall adjacent andspaced apart from the first pad face, an opposed second end walladjacent and spaced apart from the second pad face and at least onesidewall extending between the first end wall and the second end wall.

The back-up apparatus can also include a plurality of pad suction inletsthat are spaced apart from each other along a first circumference and aplurality of plate suction apertures that are spaced apart from eachother along a second, smaller circumference.

The back-up apparatus can also include a plurality of internal suctionconduits wherein an upstream end of each internal suction conduit can bein fluid communication with one pad suction aperture and a downstreamend of each internal suction conduit can be in fluid communication withone plate suction aperture.

The suction inlet can include an open suction channel provided in thesecond pad face and in fluid communication with at least one internalsuction conduit.

The upstream end of each internal suction conduit can be in fluidcommunication with one pad suction aperture and the downstream end ofeach internal suction conduit can be in fluid communication with thesuction channel.

The upstream end of each internal suction conduit can be in fluidcommunication with the suction channel and the downstream end of eachinternal fluid conduit can be in fluid communication with the at leastone plate suction aperture.

The back-up apparatus can also include an internal suction plenum withinthe back-up apparatus and in fluid communication between the platesuction aperture and the pad suction inlet.

The internal suction plenum can be in fluid communication with the platesuction aperture and each internal suction conduit can have an upstreamend in fluid communication with one pad suction inlet and a downstreamend in fluid communication with the internal suction plenum.

The internal suction plenum can be in fluid communication with each ofthe plate suction apertures and the downstream end of each internalsuction conduit.

The internal suction plenum can be a continuous channel.

In accordance with at least some of these aspects, a surface treatingapparatus can include a driving apparatus and a back-up apparatusmounted on the driving apparatus and comprising a back-up plate and aback-up pad. The back-up plate can have a pad attachment face and alongitudinally opposed rear face. The back-up plate can include acentral axis and a plate suction aperture extending through the back-upplate. The back-up pad can have a first pad face, secured to the padattachment face, and a second pad face for supporting an abrasive sheet.The back-up pad can include at least one of pad suction inlet in thesecond pad face. The surface treating apparatus can also include aninternal suction conduit extending transversely through the back-up padand connecting the pad suction inlet with the plate suction aperture.The surface treating apparatus can also include a suction housingmounted on the driving apparatus. The suction housing can have a housingsidewall radially surrounding the at least one plate suction apertureand a housing inlet adjacent to and fluidly connected to the at leastone plate suction aperture to receive sanding waste from the back-upapparatus. The housing sidewall can be radially intermediate the atleast one pad suction inlet and the at least one plate suction aperture.

The plate suction aperture can be radially spaced apart from the centralaxis by a first radial distance. The pad suction inlet can be radiallyspaced apart from the central axis by a second radial distance. Thesecond radial distance can be greater than the first radial distance.The internal suction conduit can include an upstream end in fluidcommunication with the suction inlet and a downstream end incommunication with the plate suction aperture for communication ofsanding waste through the back-up apparatus. The internal suctionconduit can be positioned longitudinally intermediate the first andsecond pad faces.

The surface treating apparatus can also include an interface layer thatcan have an inner face, fixedly fastened to the second pad face, and anopposed abrasive mounting face. The interface layer can include aninterface suction aperture registered with the at least one suctioninlet in the second pad face.

The at least one internal suction conduit can include a first end walladjacent and spaced apart from the first pad face, an opposed second endwall adjacent and spaced apart from the second pad face and at least onesidewall extending between the first end wall and the second end wall.

The at least one suction inlet can include a plurality of pad suctionapertures spaced apart from each other along a first circumference andthe at least one plate suction aperture can include a plurality of plateoutlet apertures spaced apart from each other along a second, smallercircumference. Each pad suction aperture can be fluidly connected to atleast one of the plate outlet apertures by a corresponding one of the atleast one internal suction conduits.

The upstream end of each internal suction conduit can be in fluidcommunication with one pad suction aperture and the downstream end ofeach internal suction conduit can be in fluid communication with oneplate suction aperture.

The at least one suction inlet can include an open suction channelprovided in the second pad face and in fluid communication with the atleast one internal suction conduit.

The upstream end of each internal suction conduit can be in fluidcommunication with one pad suction aperture and the downstream end ofeach internal suction conduit can be in fluid communication with thesuction channel.

The upstream end of each internal suction conduit can be in fluidcommunication with the suction channel and the downstream end of eachinternal fluid conduit can be in fluid communication with the at leastone plate suction aperture.

In accordance with another aspect of the invention, which may be used byitself or with any one or more other aspects of the invention, a surfacetreating apparatus that includes a suction system can be configured tobe compatible for use in grinding operations and for use with fibrediscs and other relatively aggressive abrasive media. The surfacetreating apparatus can include a back-up plate that is configured foruse with fibre discs, and the like, and need not include a compliant,flexible back-up pad. To facilitate suction, the back-up plate and fibredisc can include suction apertures and suction holes or apertures,respectively. The suction apertures in the back-up plate can be throughholes, or can be configured in any other suitable configuration,including, for example, having suction channels, conduits and plenums asdescribed herein.

Conventional fibre disc sanding apparatuses do not include back-upapparatuses of the nature described herein. The stiffness of the fibredisc abrasive sheets can be sufficient to be used in grinding operationswithout the need for an external back-up apparatus. Also, inconventional grinding applications, the fibre disc abrasive is notintended to follow the contours of a surface being grinded, and theflexibility of the back-up pads described herein may be unnecessary.Further conventional fibre disc sanding apparatuses also do not includesuction systems of the nature describe herein. Conventional fibre discsdo not include suction holes, and the sanding apparatuses do not includesuction housings, etc. Conventional fibre disc sanding apparatuses areoperated without a back-up apparatus suitable for connection with asuction system. Further, the coarse nature of the abrasive material usedon conventional fibre discs, and the nature of the surfaces beinggrinded, makes fibre discs less likely than conventional, fine grainsand paper to become clogged with sanding debris.

Forming suction holes in conventional fibre discs can result inaccelerated wear on the forming tools (such as a press or die) due tothe nature of the strong abrasive materials coating the fibre disc.

The inventor has discovered that fibre discs can be used in combinationwith a back-up plate. The inventor has also discovered that fibre discscan be provided with suction holes, and can be used in combination witha suction system. Providing a fibre disc mounted to a back-up plate,and/or equipped with suction holes may help improve the performance ofthe fibre disc.

In accordance with at least one of these aspects, a surface treatingapparatus can include a back-up apparatus connectable to a drivingapparatus and rotatable about a central axis. The back-up apparatus caninclude a back-up plate that can have an abrasive mounting face and anopposed rear face, and a plurality of plate suction apertures extendingthrough the back-up plate. The surface treating apparatus can alsoinclude an abrasive fibre disc. The fibre disc can have an abrasivesurface coated with abrasive material and an opposed mounting surfaceadjacent the pad attachment face of the back-up plate. The fibre disccan also include a central mounting aperture for receiving a mountingfastener for attaching the fibre disc to at least one of the back-upapparatus and the driving apparatus, and a plurality of disc suctionapertures registered with corresponding ones of the plurality of platesuction apertures. The surface treating apparatus can also include asuction apparatus that can have a suction housing. The suction housingcan include a suction housing inlet opposite the rear face of back-upplate and surrounded by a suction housing sidewall. The suction housinginlet can be in fluid communication with the plurality of plate suctionapertures for extracting sanding waste through the fiber disc andback-up apparatus.

The plurality of disc suction apertures can be spaced apart from eachother about the periphery of the fibre disc.

The plurality of disc suction apertures can be spaced an equal radialdistance from the central axis of rotation.

The plurality of plate suction apertures can be radially inboard fromthe suction housing sidewall.

The suction apparatus can include a first edge that is spaced apart fromthe rear face of the back-up plate by a suction spacing distance. Thefirst edge can be moveable relative to the back-up plate in a directionparallel to the central axis of rotation whereby the suction spacingdistance can be altered to adjust the suction strength.

The suction apparatus can include a collar coupled to the suctionhousing and translatable relative to the suction housing. The collar caninclude the first edge.

The surface treating apparatus can also include a securing apparatusconfigured to secure the collar to the suction housing therebyinhibiting relative movement therebetween. The securing apparatus caninclude a clamp.

The suction housing can be longitudinally movably coupled to the drivingapparatus, the suction housing comprising the first edge.

The first edge can be moveable while the back-up plate is rotating.

The disc suction apertures can include aperture sidewalls that are atleast partially coated with the abrasive material.

The back-up plate can be rigid.

In accordance with at least one of these aspects, a method ofmanufacturing an abrasive fibre disc can include the steps of: a)providing a sheet of base material; b) forming the base material into adisc; c) forming a central mounting aperture in the centre of the disc;d) forming a plurality of discrete suction apertures in the disc; e)after forming the central mounting aperture and the plurality of suctionapertures, coating at least one side of the disc with abrasive material.

The plurality of suction holes can be arranged on a commoncircumference.

The steps b), c) and d) can be carried out generally simultaneously.

In accordance with yet another aspect of the invention, which may beused by itself or with any one or more other aspects of the invention, asafety fastener can be used to secure an abrasive sheet to a surfacetreatment apparatus. Under certain operating conditions, for examplehigh temperatures and/or high friction between the abrasive sheet andthe surface being treated, there can be a risk that the abrasive sheetcan separate from the back-up pad. For example, the primary attachmentmechanism used to hold the abrasive sheet to the back-up apparatus, forexample hook and loop fasteners and some conventional adhesives, canweaken over time, reducing the strength of the bond with the abrasivesheet. In some applications, it can be advantageous to provide asecondary, safety fastening mechanism to secure the abrasive sheet tothe back-up pad. The safety fastening mechanism can be configured tokeep the abrasive sheet attached to the surface treating apparatus inthe event of a primary attachment mechanism failure.

Preferably, the safety fastening mechanism is releasable to facilitatechanging and replacement of the abrasive sheets, and is re-usable. Theback-up apparatus can be configured to receive the safety fasteningmechanism.

In accordance with this aspect, a back-up apparatus can include aback-up plate having a pad attachment face and an opposed rear face. Theback-up plate can include a central bore. The back-up apparatus can alsoinclude a back-up pad having a first pad face, provided on the padattachment face, and a second pad face for supporting an abrasive sheet.The back-up pad can include a pad central opening registered with thecentral bore on the back-up plate. An abrasive sheet safety fastener canbe releasably securable to the central bore and configured to secure anabrasive sheet to the back-up pad.

The back-up apparatus can also include an interface layer having aninner face, fixedly fastened to the second pad face, and an opposedabrasive mounting face. The interface layer can include an interfacecentral aperture registered with the pad central aperture and adapted toreceive the safety fastener.

The plate central bore can be internally threaded and the safetyfastener can be a bolt having mating threads.

The threads in the central bore can be formed as part of the back-upplate, or can be provided by an anchor member that is connected to theback-up plate.

The safety fastener can extend through the back-up apparatus and can beengageable with a drive spindle on a driving apparatus.

The back-up apparatus can also include a washer positionable as aninterface between the fastener and the abrasive sheet and mountable onthe fastener for non-rotational movement with respect to the back-up padas the fastener is secured in to the central bore whereby damage to thefastener from the abrasive material is inhibited.

The back-up apparatus can be configured so that a head of the fasteneris recessible below a plane containing the abrasive mounting surfacewhen the fastener is secured to the central bore.

The back-up pad can be compressible and is compressed when the safetyfastener is tightened.

In accordance with another aspect of the invention, which may be used byitself or with any one or more other aspects of the invention, amounting tool can be used to place an abrasive sheet on a correspondingback-up apparatus. Obtaining proper radial and rotational alignmentbetween an abrasive sheet and a back-up apparatus can be challengingwhen the abrasive sheet is attached by hand. It can be advantageous toproperly align the abrasive sheet on the back-up apparatus. Improperradial or lateral alignment can cause imbalances and vibrations when thesurface treatment apparatus is use. Improper rotational alignment canresult in improper registration of the suction holes in the abrasivesheet with the suction apertures in the back-up pad, which may impedesuction performance. Placing the abrasive sheet on the back-up apparatusmay be particularly challenging when the suction apparatus is active, asthe suction from the pad suction apertures may tend to pull the abrasivesheet against the back-up pad before it can be properly aligned.

It may be advantageous to provide a mounting tool that can be used toassist a user when attaching an abrasive sheet to a back-up pad,particularly when the abrasive sheet includes suction holes. It may bedesirable to have a mounting tool that can be used when the suctionapparatus is active.

For example, in instances when the back-up pad includes a plurality ofdiscrete pad suction apertures in the abrasive mounting face (instead ofor in addition to an open suction channel), it may be advantageous touse an abrasive sheet mounting tool to help facilitate placement of anabrasive sheet on the back-up pad. Alternatively, if the back-up padincludes an open suction channel, the mounting tool can be configured sothat it is compatible with the open suction channel.

In accordance with at least one of these aspects, a tool for mounting anabrasive sheet having a plurality of sheet suction apertures arranged ina first pattern on a back-up pad comprising at least one correspondingpad suction inlet configured to be registered with the plurality ofsheet suction apertures, can include a body that can include a handleportion. The tool and also include a plurality of alignment pinsextending from pin attachment locations on the body. The plurality ofalignment pins can be positioned to match the first pattern so that eachone of the plurality of alignment pins can be aligned with acorresponding one of the plurality of sheet suction apertures to receivethe abrasive sheet. Each support pin can be insertable into the at leastone pad suction inlet while the abrasive sheet is supported on thealignment pins.

The alignment pins can be moveably mounted to the body.

The alignment pins can be securable to alternate pin attachmentlocations.

The body can include multiple sets of pin attachment locationscorresponding to multiple abrasive sheet suction aperture patternswhereby the alignment pins can be positioned to match the plurality ofdifferent sheet suction aperture patterns.

Each alignment pin can extends from a first end proximate the body to asecond distal end. The distal end of each alignment pin can be contouredto facilitate insertion of the pins into the pad suction apertures.

The tool can include three alignment pins arranged in a generallytriangular configuration.

The alignment pins can lie on a common circumference.

The cross-sectional shape of each alignment pin can correspond to ashape of the sheet suction apertures.

The alignment pins can be sized to be smaller than the abrasive sheetsuction apertures so that the abrasive sheet can slide along the lengthof the alignment pins when the alignment pins are inserted into the atleast one pad suction inlet.

The plurality of alignment pins can be sized to be freely removable fromboth the abrasive sheet suction apertures and the at least one padsuction inlet when the abrasive sheet is attached to the back-up pad.

In accordance with at least one of these aspects, a method of mountingan abrasive sheet having a plurality of sheet suction apertures on aback-up pad comprising a at least one corresponding pad suction inletcan include the steps of a) aligning at least a portion of the sheetsuction apertures with alignment pins on a mounting tool; b) sliding theabrasive sheet onto the mounting tool; c) aligning the alignment pinswith the at least one pad suction inlet and inserting the alignment pinstherein, thereby aligning the plurality of sheet suction apertures withthe plurality of pad suction apertures; d) securing the abrasive sheetto an abrasive mounting face of the back-up pad; and e) removing thealignment pins from the respective ones of the pad suction apertures.

The method can include the step of positioning the alignment pins on themounting tool to align so as to be alignable with the suction sheetapertures.

In accordance with another aspect of the invention, which may be used byitself or with any one or more other aspects of the invention, a back-upapparatus can include a back-up plate that is generally planar.Optionally, the back-up plate can be free from integrated hardware.Conventional back-up plates tend to have 3D, or non-planarconfigurations, and are formed from injection molded plastic. Mountinghardware is often molding into the part. The rear surfaces ofconventional back-up plates can vary from plate to plate, and betweensizes of back-up apparatuses. The differences in the configuration ofthe back-up plates can make it difficult to provide a suction apparatusthat is compatible with multiple styles and sizes of back-up apparatus,optionally for different purposes.

Injection molding back-up plates can be relatively expensive. Designchanges to molded back-up plates can require changes to thecorresponding molds, dies etc. Forming back-up plates from a planarsheet of material can be relatively lower cost than injection molding,and can allow for increased design flexibility.

In the examples describe previously, the back-up plate is generally morerigid than the back-up pad. Optionally, the back-up plate can be formedfrom molded plastic. In such a configuration, the back-up plate may havea curved, three-dimensional rear face (facing away from the back-uppad).

Alternatively, according to this aspect, the back-up plate can be agenerally planar member, having a generally planar, or two-dimensional,rear face. Providing a planar rear face may help reduce the amount ofmaterial required to form the back-up plate.

Providing a planar rear face may also help standardize the axialdimensions/configurations of different sized back-up plates.Standardizing the size and shape of the rear face may help facilitatethe use of the same auxiliary equipment, such as the suction housing,with a variety of back-up plates of different sizes. This configurationmay allow a user to quickly change the back-up apparatus on a sandingapparatus (for example from an eight inch grinding abrasive to a sixinch sanding abrasive) without having to adjust or reconfigure thesuction housing, and optionally other equipment.

Planar back-up plates may also be easier and/or less expensive tomanufacture than an analogous mold plastic back-up plate. The materialused in the planar back-up plate can be selected that it is more warpresistant than conventional molded back-up plates. The back-up plate canbe formed in any suitable shape for use with a variety of surfacetreating apparatuses, and need not be limited to circular or disc-likeplates.

In accordance with this aspect, a back-up apparatus can include aback-up plate having a planar pad attachment face, a parallel, opposedplanar rear face, and a central plate aperture sized to removablyreceive a mounting fastener. The back-up apparatus can also include aback-up pad having a first pad face, provided on the pad attachmentface, and a second pad face for supporting an abrasive sheet, and acentral pad aperture extending from the first pad face to the second padface and registered with the central plate aperture. The central padaperture can be sized to removably receive the mounting fastener.

The plate can be formed from a rigid composite material.

The plate can have a tensile strength of between about 40 MPa to about80 MPa and a Young's modulus of between about 1.8 GPa and about 2.5 GPa.

The plate can be formed from polycarbonate.

Also in accordance with this aspect, a method of manufacturing a back-upplate can include the steps of: a) providing a planar sheet of platematerial; b) forming a back-up plate from the sheet of plate material;and c) forming a central mounting aperture in the back-up plate toaccommodate a mounting fastener.

Step b) can include cutting the back-up plate from the planar sheet.

The back-up plate can have a plate radius and the method can includeselecting the plate radius to be smaller than a pad radius of a back-uppad that is to be coupled to the back-up plate.

The method can also include forming a plurality of plate suctionapertures in the back-up plate.

The steps of forming the back-up plate, forming a central mountingaperture and forming the plurality of plate suction apertures can beperformed substantially simultaneously.

Also in accordance with this aspect, a method of manufacturing a back-upapparatus can include the steps of: a) providing a back-up pad having apad radius and a central pad aperture; b) providing a planar sheet ofplate material; c) forming a back-up plate having a plate radius fromthe sheet of plate material the plate radius being equal to or smallerthan the pad radius; d) forming a central plate aperture in the back-upplate to accommodate a mounting fastener; e) applying adhesive to aleast one of a first pad face of the back-up pad and a pad attachmentface of the back-up plate; f) aligning the first pad face of the back-uppad and the pad attachment face so that the central pad aperture isregistered with the central plate aperture; and, g) bonding the firstpad face to the pad attachment face.

In accordance with another aspect of the invention, which may be used byitself or with any one or more other aspects of the invention, anauxiliary member can be positioned between the back-up pad and theabrasive sheet. The auxiliary member can be permanently or removablyattached to the back-up apparatus. Providing an auxiliary member canallow a user to modify the properties of the back-up apparatus. Oneexample of an auxiliary member is a sponge member that is generallysofter and more compliant than the back-up pad to which it is mounted.

DRAWINGS

The drawings included herewith are for illustrating various examples ofarticles, methods, and apparatuses of the teaching of the presentspecification and are not intended to limit the scope of what is taughtin any way.

In the drawings:

FIG. 1 is a perspective view of a sanding apparatus;

FIG. 2 is a rear perspective of a back-up apparatus from the sandingapparatus of FIG. 1;

FIG. 3 is a partially exploded side view of the back-up apparatus ofFIG. 2;

FIG. 3A is a detail view of region 3A shown in FIG. 3;

FIG. 4 is a partially exploded side view of an abrasive sheet useablewith the back-up apparatus of FIG. 3;

FIG. 4A is a detail view of region 4A in FIG. 4;

FIG. 5 is a perspective view of another example of a sanding apparatus;

FIG. 6 is a section view take along line 6-6 in FIG. 5;

FIG. 7 is a rear perspective view of the back-up apparatus shown in FIG.5;

FIG. 8 is a front perspective view of the back-up apparatus of FIG. 7;

FIG. 9 is a section view taken along line 9-9 in FIG. 7;

FIG. 10 is a partially exploded perspective view of another example of aback-up apparatus and an abrasive sheet;

FIG. 11 is a section view taken along line 11-11 in FIG. 10;

FIG. 12 is a partially exploded perspective view of another example of aback-up apparatus and an abrasive sheet;

FIG. 13 is an exploded view of the back-up pad of FIG. 12;

FIG. 14 is a section view taken along line 14-14 in FIG. 12;

FIG. 15 is a perspective view of another example of a back-up apparatusand an abrasive sheet;

FIG. 16 is a partial section view of another example of a sandingapparatus;

FIG. 17 is a perspective view of an abrasive sheet mounting tool;

FIG. 18 is a rear perspective view of the abrasive sheet mounting toolof FIG. 17;

FIG. 19 is a side view of the abrasive sheet mounting tool of FIG. 17,in combination with an abrasive sheet and a back-up apparatus;

FIG. 20 is a perspective view of another example of an abrasive sheetmounting tool;

FIG. 21 is a perspective view of the abrasive sheet mounting tool ofFIG. 20, in combination with an abrasive sheet and a back-up apparatus;

FIG. 22 is a plan view of the of the abrasive sheet mounting tool ofFIG. 20;

FIG. 23 is a rear perspective view of a back-up apparatus;

FIG. 24 is a section view taken along line 24-24 in FIG. 23;

FIG. 25 is a perspective view of a sheet of back-up plate material;

FIG. 26 is a perspective view of another example of a sanding apparatus,with a driving apparatus shown in phantom;

FIG. 28 is a partially exploded view of the back-up apparatus andsuction apparatus of FIG. 26;

FIG. 28 is a section view taken along line 28-28 in FIG. 26; and,

FIG. 29 is partially exploded side view of another example of a back-upapparatus.

Elements shown in the figures have not necessarily been drawn to scale.Further, where considered appropriate, reference numerals may berepeated among the figures to indicate corresponding or analogouselements.

DETAILED DESCRIPTION

Various apparatuses or processes will be described below to provide anexample of an embodiment of each claimed invention. No embodimentdescribed below limits any claimed invention and any claimed inventionmay cover processes or apparatuses that differ from those describedbelow. The claimed inventions are not limited to apparatuses orprocesses having all of the features of any one apparatus or processdescribed below or to features common to multiple or all of theapparatuses described below. It is possible that an apparatus or processdescribed below is not an embodiment of any claimed invention. Anyinvention disclosed in an apparatus or process described below that isnot claimed in this document may be the subject matter of anotherprotective instrument, for example, a continuing patent application, andthe applicants, inventors or owners do not intend to abandon, disclaimor dedicate to the public any such invention by its disclosure in thisdocument.

A surface treating apparatus can be used for treating a surface, forexample by sanding, grinding, polishing and the like. Examples ofsurface treating apparatuses, and methods for using such apparatuses aredescribed below. The term surface treating apparatus can includesanders, grinders, polishers, buffers and any other like apparatus. Forsimplicity, embodiments described below by way of example may bedescribed as sanding apparatuses or grinding apparatuses, etc, but thefeatures described as being incorporated into a “sanding apparatus”, forexample, can also be incorporated into other suitable surface treatingapparatuses, and vice versa.

Structure of a Sanding Apparatus

Referring to FIGS. 1 and 2, an example of a sanding apparatus 100includes a driving apparatus 102 and a back-up apparatus 104. Theback-up apparatus 104 has a rear face 106 (facing the driving apparatus)and an opposed abrasive mounting face 108. An abrasive sheet 110 isreleasably attachable to the abrasive mounting face 108. The releasableengagement between the abrasive sheet 110 and the abrasive mounting face108 may help facilitate the replacement of a used or worn abrasive sheet110 with a new, replacement abrasive sheet 110 or an abrasive sheet witha different grit.

In the illustrated example, the abrasive sheet 110 is attached to theabrasive mounting face 108 using a releasable, reusable adhesive.Alternatively, the abrasive sheet 110 can be attached to the abrasivemounting face 108 using any suitable, releasable fastener including, forexample, adhesives and mechanical fasteners (including, for example,hook and loop fasteners or a locking clamp).

The driving apparatus 102 can be any suitable type of driving apparatusthat is compatible with the back-up apparatus, including, for example arotary driving apparatus (including, for example electric andair-powered rotary drivers and grinders), and a double action drivingapparatus.

The abrasive sheet 110 can be any suitable type of surface treatingproduct that is used to treat a surface, such as by sanding, grinding,polishing or buffing a surface, including, for example, sand paper,resin cloth abrasive discs, fiber discs, and waterproof sandpaper andother like surface treatment products. Accordingly, as used herein, theterm sanding apparatus relates to any apparatus that is used incombination with a suitable abrasive material, including, for example,sanders, grinders, polishers and buffers, and is not limited apparatusesequipped with conventional sand paper. It will be appreciated that whileabrasive sheet may be disc shaped as exemplified, it may be any othershape, such as square or rectangular is used with a double actiondriving apparatus.

Referring to FIGS. 2 and 3, in the illustrated example the back-upapparatus 104 includes a back-up plate 112 and a back-up pad 114.

The back-up plate 112 has a back face 116 and an opposed pad attachmentface 118. In the illustrated example, the back face 116 of the back-upplate 112 comprises the rear face 106 of the back-up pad 104. The padattachment face 118 is adapted to be coupled to the back-up pad 114.Preferably, the back-up plate 112 is formed from a relatively rigidmaterial, including, for example, metal, plastic and compositematerials.

The back-up pad 114 is preferably formed from a material that isrelatively more flexible than the back-up plate 112. For example, in theillustrated embodiment the back-up pad 114 is made from a resilientlyflexible material such as a natural or a synthetic rubber.

The back-up pad 114 includes a first pad face 120 and an opposed secondpad face 122. The first pad face 120 abuts the pad attachment face 118of the back-up plate 112. Preferably, the first pad face 120 ispermanently attached to the pad attachment face 118, for example, by alayer of permanent adhesive. Optionally, the second pad face 122 can becoupled to directly to an abrasive sheet 110, or, in accordance with oneaspect of this specification, to an interface layer 124, which may bedirectly bonded to the abrasive sheet 110. Examples of suitableinterface layers include a mechanical attachment layer (e.g. a layercomprising hooks or loops of a hook and loop fastener system) and anadhesive interface layer.

Interface Layer

In accordance with one aspect of this specification, which may be usedby itself or with any one or more other aspects of this specification,an interface layer is used to secure an abrasive sheet 100 to a back-uppad 114. The back-up pad 114 provides a mounting support for theabrasive sheet 110 and, preferably, provides a cushioned backing. Duringuse, an abrasive sheet is subjected to substantial forces in the planeof the abrasive sheet. If the adhesive used to secure the abrasive sheetin place is too weak, then the sheet may become dislodged during use andthis may mar or otherwise spoil the surface being treated. If theadhesive is too strong, it may be difficult to remove worn abrasivesheets from the back-up pad, and/or portions of the abrasive sheet maytear and remain fixed to the back-up pad. An advantage of the interfacelayer is that it may provide a stronger, releasable attachment of theabrasive sheet to the back-up pad.

Referring also to FIG. 3 a, in the illustrated example, the back-upapparatus 104 includes an adhesive interface layer 124. The adhesiveinterface layer 124 includes, and preferably is, a porous sheet 126. Theporous sheet 126 has an inner face 128 that may be permanently glued orotherwise secured to the second pad face 122, and an opposed outer face130 that can be releasably attached to the abrasive sheet 110. Theinterface layer 124 is preferably flexible so as to move and flex withthe back-up pad 114 during use. In this example, the outer face 130 ofthe interface layer forms the abrasive mounting face 108 of the back-upapparatus 104.

The porous sheet 126 has a surface that is textured thereby providingspaces that are recessed in the Z direction (which can be generallyperpendicular to the plane comprising the abrasive mounting face 108)for receiving an adhesive applied thereto. An advantage of porous sheet126 an adhesive may penetrate into the openings in the porous sheet 126and thereby provide a greater surface area for the adhesive to besecured to porous sheet 126. The interface layer may absorb the baseadhesive such that the adhesive extends at least partially into theinterface layer and coats its fibres. Accordingly, some or all of thefibres in the interface layer may be saturated or coated with the baseadhesive.

Preferably, the porous sheet 126 is a lofty or pile fabric material thathas a plurality of individual fibres 132 extending away from the outerface 130. An example of such a material is a loop material such as maybe used in a hook and loop fastener system. Examples of other suitablematerials include felt, wool-based fabrics and cotton-based fabrics, orany other material that has fibres provided on at least one surface of asubstrate.

To provide a re-usable, releasably adhesive surface suitable for bondingto the abrasive sheet 110, the abrasive mounting face 108 is coated withat least one and preferably two discrete adhesive layers.

To manufacture a suitable adhesive interface layer 124, the abrasivemounting face 108 may be first coated with a layer of a first or baseadhesive 134. The base adhesive 134 can be a partially setting adhesiveand may be applied over all or substantially all of the abrasivemounting face 108. Preferably, the base adhesive 134 is thenmechanically worked into the porous sheet 126, such as by brushingand/or rolling the base adhesive into the porous sheet 126. Working theadhesive into the porous sheet 126 may help coat the individual loopfibres 132 extending from the outer face 130 and may provide athree-dimensional adhesive coating, for example, a coating that coversthe surface of the outer face 130 and permeates at least partially intothe thickness 136 of the porous sheet 126. Coating the fibres 132 inthis manner may help increase the available adhesive surface area of thebase adhesive layer 134, and may help strengthen the adhesive bondbetween the base adhesive layer 134 and the porous sheet 126 (forexample, as compared to a conventional “surface” or two-dimensionalcoating of adhesive).

After working the base adhesive 134 into the porous sheet 126, theadhesive interface layer 124 can be allowed to dry to at least partiallyset or cure the base adhesive 134. Preferably, the adhesive interfacelayer 124 is allowed to dry until the base adhesive 134 is fully cured.

The base adhesive may be any adhesive that may flow or be worked intothe openings in porous sheet 126.

When the base adhesive 134 is sufficiently cured, a layer of a second ortacky adhesive 138 may be applied over the base adhesive 134.

Optionally, the base and tacky adhesives 134, 138 are selected so thatthey are compatible with each other, such that the tacky adhesive 138will firmly and permanently bond with the base adhesive 134. Applyingthe tacky adhesive 138 after the base adhesive 134 has at leastpartially cured may help inhibit mixing of the adhesives 134, 138 whilethey are wet.

The tacky adhesive 138 can be any suitable adhesive that will bond withthe base adhesive 134, and will remain sufficiently tacky to releasablybond to one or more abrasive sheets 110 for an extended period of time.For example, the tacky adhesive 138 can be selected so that under normaloperating conditions, it can remain releasably and reusably tacky forseveral weeks, months or years, having been through a plurality ofabrasive sheet changes.

The tacky adhesive 138 is also selected so that it maintains asufficient degree of tackiness to prevent separation of the abrasivesheet when elevated to the expected operation temperatures of theback-up apparatus 104, which may be, for example, between about 25° C.and about 250° C. or between about 35° C. and about 100° C. (for examplefor light to medium sanding operations) and optionally between about 30°C. and about 500° C. to about 800° C. or higher (for example for heavysanding or grinding operations). For example, the adhesive can beselected so that it maintains its bond strength when a steel materialthat is being grinded glows red hot. Preferably, the high-temperaturebond strength between the tacky adhesive 138 and the abrasive sheet 110is at least about 80% of the standard, or room temperature, bondstrength, and preferably can be at least about 90% or 95% of the roomtemperature bond strength. The tacky adhesive may be any adhesive thatis suitable for bonding with the back of the abrasive sheet, and ispreferably a Mylar® compatible adhesive if the abrasive sheet 110includes a Mylar® film.

In addition, the tacky adhesive 138 is selected so that the strength ofthe adhesive bond between the base adhesive 134 and the tacky adhesive138 is greater than the strength of the adhesive bond between the tackyadhesive 138 and the abrasive sheet 110. In this configuration, wornabrasive sheets 110 can be repeatedly peeled off of the abrasivemounting face 108 without transferring the tacky adhesive 138 from theinterface layer 124 to the abrasive sheet 110.

In the illustrated example, the back-up pad 114 tapers towards itsperipheral edge, and second pad face 122 has a larger surface area thanthe first pad face 120. In this configuration the back-up pad 114thickness decreases from a first thickness 140 toward the centre of theback-up pad 114, to a second, thinner thickness 142 toward theperipheral edge of the pad 114. Reducing the thickness at the edge ofthe back-up pad 114 may help increase the flexibility of the peripheralportions of the back-up pad 114. In the illustrated example, theinterface layer 124 is generally coterminous with the second pad face122, and has a surface area that is greater than the first pad face 120.

Referring to FIGS. 4 and 4A, an abrasive sheet 110 that is suitable foruse with the adhesive interface layer 124 described above includes abase sheet 144, a layer of abrasive material 146 coated on one side ofthe base sheet and a film layer 148 bonded to the opposed side of thebase sheet 144. The base sheet 144 can be any suitable material,including for example, paper and cloth.

The film layer 148 is permanently bonded to the base sheet 144, forexample using adhesive layer 150. Adhesive layer 150 may be any adhesivethat is compatible with both the base sheet 144 material and the filmlater 148 material used in a given abrasive sheet, to permanently bondthe base sheet 144 to the film layer 148.

The film layer 148 provides a mounting surface, which is preferablysmooth, for bonding to the abrasive mounting face 108 on the adhesiveinterface layer 124. Preferably, the film layer 148 and the tackyadhesive 138 are mutually selected such that the film layer isreleasably securable to the tacky adhesive. For example, the tackyadhesive may act like contact cement formulated to be provided on onlyone surface. Optionally, an adhesive, which is releasably securable tothe tacky adhesive 138, may be applied to the inner surface of the filmlayer 148

In the illustrated example, the bond between the tacky adhesive 138 andthe film layer 148 has sufficient strength to retain the abrasive sheet110 during use, without requiring any additional adhesive material to beprovided on the film layer 148. In this example, the abrasive sheets 110can be manufactured without having any exposed adhesive on the outersurface of the film layer 148. This may eliminate the need for providingrelease cover sheets, for example wax paper sheets, on the back of theabrasive sheets 110, as is generally required when producing andhandling adhesive-coated abrasive sheets.

Preferably, the film layer 148 is made from Mylar® nylon or anothersimilar strong plastic-like material that can provide a satisfactorilysmooth mounting face. Providing a rough surface to contact the tackyadhesive 138 may undesirably increase the strength of the adhesive bondbetween the abrasive sheet 110 and the tacky adhesive 138. The requireddegree of smoothness of the film layer 148 is selected based on theproperties of the tacky adhesive used, so that the bond between the filmlayer 148 and the tacky adhesive 138 is weaker than the bond between thetacky adhesive 138 and the base adhesive 134.

Providing a smooth mounting face may help control the strength of theadhesive connection between the film layer 148 and the interface layer124. Providing a smooth surface may also help seal the connectionbetween the abrasive sheet 110 and the interface layer 124, to inhibitthe admission of dust and other debris between the film layer 148 andthe interface layer 124.

The material of the film layer 148 can be selected such that it isstronger than the base layer 144 of the abrasive sheet 110. Providing arelatively stronger film layer 148 may help increase the overallstrength of the abrasive sheet 110 and may help limit tearing of theabrasive sheet 110 during use and when peeling a worn abrasive sheet 110off of the adhesive interface layer 124.

To replace a worn abrasive sheet 110, a user can first separate the wornabrasive sheet 110 from the interface layer 124 by peeling the filmlayer 148 from the abrasive mounting face 108. The user can then alignthe film layer 148 of a replacement abrasive sheet 110 with the abrasivemounting face 108 of the interface layer 124, and pressing the filmlayer 148 against the interface layer 124 to secure the abrasive sheet110 to interface layer 124. This process can be repeated for subsequentabrasive sheet 110 replacements.

Preferably, the abrasive sheet 110, including the film layer 148, isrelatively flexible and can move and flex with the back-up pad 114, forexample, to help follow the surface contours of an object or surfacebeing sanded.

As an alternative to the adhesive interface layer 110 described above, amechanical interface layer, such as a layer of “hook” material, can beused to support an abrasive sheet 110 that includes a layer ofcomplimentary loop material, or vice versa.

Open Suction Channel

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, the back-up apparatus has an open sided channel in theouter face thereof, the open sided channel is configured to connect aplurality of suction openings in an abrasive sheet in fluidcommunication with a source of suction. For example, the open sidedchannel may overlie at least two suction openings in an abrasive sheetand, preferably, may overlie all of the suction openings in an abrasivesheet. Accordingly, the rotational alignment of the abrasive sheetduring the mounting of the abrasive sheet to the back-up pad may besimplified and optionally may be eliminated.

Optionally, a surface treating apparatus can be configured to include asuction system. The suction system can be operable to extract dust andother particulate matter from the region between the abrasive sheet andthe surface being sanded. Removing debris from the surface using thesuction system may help inhibit clogging or fouling of the abrasivesheet, and may help improve sanding performance.

Referring to FIGS. 5 and 6, a sanding apparatus 1100 includes a drivingapparatus 1102 a back-up apparatus 1104 and a suction apparatus 1152.The sanding apparatus 1100 may be generally similar to the suctionapparatus 100, and like features are illustrated using like referencenumerals starting at 1100. The sanding apparatus 1100 is a double actionsanding apparatus, and the back-up apparatus 1104 has a central axis1154.

In the illustrated example, the suction apparatus 1152 includes anoptional suction housing 1156 that is mounted on the driving apparatus1102. The suction housing 1156 can be non-movably fixed relative to thedriving apparatus 1102, and includes a housing end wall 1158 and ahousing sidewall 1160. The suction housing 1156 can be made from anysuitable material having sufficient mechanical strength to resist thesuction forces within the housing, including, for example, metal andplastic. The suction housing connects the suction outlets on the back-upapparatus to a source of suction and may be of any design known in theart.

As exemplified, the housing sidewall 1160 extends from the housingendwall 1158 toward the back-up apparatus 1104. The sidewall 1160 may beintegral with the endwall 1158, or optionally, may be provided as aseparate member. The region surrounded by the terminal edge 1162 of thesuction housing 1156 defines a suction housing inlet 1164.

A suction housing outlet 1166 is provided in the housing sidewall 1160(or alternatively in the housing endwall 1158 or any other suitablelocation). The suction outlet 1166 can be configured to be connectableto an external suction source, including, for example, a portable vacuumor a shop vacuum line 1168) and is in fluid communication with thesuction housing inlet 1164. Optionally, a suction control member (notshown) can be positioned upstream from the suction housing outlet 1166.The suction control member can be used to regulate the suction suppliedto the suction apparatus 1152, and can be any suitable apparatus,including, for example, a valve. Optionally, the suction control membercan be operable to completely shut off the suction supplied to thesuction apparatus 1152.

In some instances it may be desirable to provide access to the interiorof the suction housing 1156. Accessing the interior of the suctionhousing 1156 may facilitate attachment and removal of a back-upapparatus and/or allow for servicing, cleaning and maintenance.Accordingly, the suction housing 1156 may optionally include amaintenance opening 1170 in the housing sidewall 1160. The maintenanceopening 1170 can allow a user to access the interior of the suctionhousing 1156, for example, to attach and/or detach the back-up apparatus1104 from the driving apparatus 1102. Optionally, the maintenanceopening 1170 can be covered with a movable cover 1172 (which may be allor part of a wall). A gasket or the like may be provided to provide anairtight seal between the cover and the opening.

Referring also to FIG. 9, the height 1174 of the suction housingsidewall 1160 can be selected so that the first edge 1162 of the suctionapparatus 1156 is spaced apart from the back-up plate 1112 by a suctionspacing distance 1176. In this configuration a gap is created betweenthe terminal edge 1162 of the suction apparatus 1156 and the rear face1106 of the back-up apparatus 1104. Providing a gap can help preventcontact between the suction apparatus 1156 and the back-up apparatus1104, which may otherwise inhibit relative movement of the back-upapparatus 1104. The height 1176 of the gap can be selected so thatcontact with the back-up plate 1112 is avoided and air flow through thegap is sufficiently throttled to help ensure a useable amount of suctionremains for extracting debris through the back-up apparatus 1104. Thesuction spacing distance 1176 can be between about 0.5 mm and about 15mm, and is preferably between about 1 mm and about 10 mm.

Configuration of an Adjustable Suction Apparatus

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, the suction spacing distance can be adjustable. Adjustingthe suction spacing distance can help regulate the amount of suctionapplied via the back-up apparatus. If the applied suction is too strong,the back-up apparatus may become non-rotatably stuck to the surfacebeing treated. This may inhibit the surface treating operation and maymar or otherwise damage the surface. If the applied suction is too weak,it may be ineffective at capturing dust and debris generated by thesurface treating process.

Optionally, the suction spacing distance can be configured to encourageat least some suction air flow to enter the suction housing via the gapbetween the housing and the back-up plate. In this configuration, thesuction apparatus may be able to capture dust and debris escaping fromthe perimeter of the back-up apparatus, and draw the debris into thesuction housing. This type of suction can be used in combination withthe suction passages that extend through the back-up apparatus.

Optionally, the surface treating apparatus 1100 can include one or morespacer elements that can be positioned between the back-up plate 1112and the driving apparatus 1102. By varying the number of spacer elementsused, the distance between the back-up plate 1112 and the drivingapparatus 1102 can be modified. If the suction housing 1156 is mountedon the driving apparatus 1102, changing the distance between the back-upplate 1112 and the driving apparatus 1102 also changes the distancebetween the back-up plate 1112 and the first edge 1162. Examples ofsuitable spacers include washer-like discs that can fit around thefastener used to secure the back-up apparatus to the driving apparatusspindle, and can abut both the spindle housing and the back-upapparatus.

Alternatively, or in addition, the suction housing 1156 can beadjustable such that the first edge 1162 is moveable relative to thedriving apparatus 1102. Examples of suction apparatus having adjustableor moveable edges are set out below.

The back-up apparatus 1104 includes at least one suction passage forfacilitating air flow communication between the surface being sanded andthe suction housing 1156. Referring to FIG. 7, in the present example,the back-up apparatus 1104 includes a plurality of plate suctionapertures 1178 formed in the back-up plate 1112. Referring also to FIG.9, the plate suction apertures 1178 can be positioned so that they arewithin the perimeter of the suction housing sidewall 1160 (e.g. locatedradially inward from the housing sidewall 1160), and are in fluidcommunication with the suction housing inlet 1164. In the illustratedexample, the back-up plate 1112 includes six plate suction apertures1178. Optionally, the back-up plate 1112 can include a different numberof plate suction apertures 1178, including between one and six suctionapertures, and more than six suction apertures (for example 8, 10 or 11suction apertures). The number of plate suction apertures can beselected based on a variety of factors, including, for example, size ofthe back-up apparatus, the type of abrasive material used, the nature ofthe surface being treated and the configuration of the suction housing1156.

In contrast to the present example, in a conventional double actionsanding apparatus, a conventional back-up pad may include acorresponding plurality of through-holes extending generally straight(longitudinally) through the back-up pad and aligned with the platesuction apertures. An abrasive sheet that is suitable for use with aconventional back-up pad may include a corresponding plurality ofsuction holes. In the conventional apparatus, before the abrasive sheetcan be attached to the conventional back-up pad the plurality of suctionholes in the abrasive sheet should be rotationally aligned with thethrough-holes in the back-up pad. Aligning the abrasive sheet in thismanner can be challenging and time consuming, particularly if thesuction system is active during the abrasive sheet replacement. Forexample, a slight rotational misalignment between the abrasive sheet andthe back-up pad can result in some or all of the suction holes beingaligned with a portion of the abrasive mounting face, instead of thesuction holes in the back-up pad. This can inhibit the suction ofdebris.

Referring also to FIG. 8, in contrast to conventional systems, theback-up pad 1114 in accordance with this aspect includes a suctionchannel 1180 that is in fluid communication with the plurality of platesuction apertures 1178. Preferably, the suction channel 1180 is apassage that is configured to provide fluid communication between theplate suction apertures 1178 and the abrasive sheet 1110. In theillustrated example, the suction channel 1180 is an open channel thatextends through the back-up pad 1114 and is aligned with an interfacesuction opening 1182 in the corresponding interface layer 1124. Thesuction channel 1180 has a depth that is generally equal to thethickness of the back-up pad 1114. Optionally, at least a portion of thesuction channel 1180 can be formed in, and/or extend into the back-upplate 1112.

The suction channel 1180 is an open channel that opens to the second padface 1122, and the interface suction opening 1182 in the overlyinginterface layer 1124. While illustrated as a generally annular channel,the size and shape of the suction channel 1180 can be selected based onthe configuration of the plate suction apertures 1178 and the suctionholes 1184 in the abrasive sheet 1110. Preferably, the shape of thesuction channel 1180 is generally symmetrical in the lateral or radialdirection, so that a portion of the channel 1180 can overlie suctionholes in the abrasive sheet 1110 in a variety of relative rotationalpositions between the abrasive sheet 1110 and the back-up apparatus1104.

In the illustrated example, the suction channel 1180 is positioned sothat it aligns with the suction holes in a multi-hole abrasive sheet1110. This may allow the back-up pad 1114 to be used with existingmulti-hole abrasive sheets (for example sheets intended for use withconventional, through-hole back-up pads). Alternatively, the pattern ofholes in the abrasive sheet 1110 and the suction channel 1180 may beselected in any mutually compatible configuration, which is differentthan the configuration of conventional multi-hole abrasive sheets.

Preferably, any layers positioned between the back-up pad 1114 and theabrasive sheet 1110 will include an opening that generally correspondsto the shape of the suction channel 1180. Providing openings in suchlayers may facilitate the desired suction air flow communication betweenthe abrasive sheet 1110 and the suction housing 1156. For example, inthe illustrated example, the interface layer 1124 used in combinationwith the back-up pad 1114 includes a corresponding suction opening 1182that is sized and shaped to generally match the open face of the opensuction channel 1180. In the illustrated example, the suction opening1182 in the interface layer 1124 is a generally annular or ring-likeopening, concentric with the central axis 1154.

The suction channel 1180 may have any shape that is suitable for usewith the suction openings in a corresponding abrasive sheet. Preferably,the suction channel 1180 is shaped so that it extends generallycontinuously around the second pad face 1122 at a radial distance 1186from the central axis 1152 that coincides with the radial spacing 1188of the suction holes 1184 in the abrasive sheet 1110. In thisconfiguration, the plurality of suction holes 1184 in the abrasive sheet1110 may be registered with the suction channel 1180 regardless of therotational position of the abrasive sheet 1110 to the back-up pad 1114.This may help ensure that each suction hole 1186 in the abrasive sheet1110 overlies the channel 1180 and is in fluid communication with thesuction apertures 1178 in the backing plate 1112, which may helpfacilitate debris removal. This may also lessen the likelihood that oneor more of the suction holes 1186 in the abrasive sheet 1110 will beblocked by or overlap the abrasive mounting face 1108.

In the illustrated example, the suction channel comprises 1180 a channelendwall 1190 disposed between the abrasive mounting face 1108 and thefirst pad face 1120, a first or inner channel sidewall 1192 extendingfrom the channel endwall 1190 to a first channel edge 1194 on the secondpad face 1122 and a second or outer channel sidewall 1196 extending fromthe channel endwall 1190 to a second channel edge 1198 on the second padface. Alternatively, the endwall of the channel 1180 may be disposedlongitudinally behind the first pad face, for example within the back-upplate 1112 (i.e. whereby the first pad face is longitudinallyintermediate the endwall 1190 and the abrasive mounting face 1108).

In the illustrated example the suction channel 1180 is generallyU-shaped in cross section and opens toward the abrasive mounting face1108. Alternatively, the suction channel can have anothercross-sectional shape, including, for example V-shaped, C-shaped,polygonal, square and arcuate.

The first and second channel edges 1194, 1198 are separated by a channelwidth 1200. The channel width 1200 can be any suitable width that iscompatible with the plate suction apertures 1178, the interface suctionopening 1182 and the suction holes 1184 in the abrasive sheet.Preferably, the channel width 1200 is generally equal to or greater thanan aperture width 1202 (FIG. 7) of the plurality of plurality of platesuction apertures 1178. This may help facilitate fluid flow from thesuction channel 1180, through the plate suction apertures 1178 and intothe suction housing 1156. Alternatively, the suction channel width 1200may be less than the diameter of the plate suction apertures. Theapertures width 1202 and the channel width 1200 can each be betweenabout 1 mm and about 60 mm, and are preferably between about 8 mm andabout 25 mm. Optionally, the channel width 1200 can be between about 1%and about 25% of the diameter of the back-up pad 1114, and preferably isbetween about 3% and about 10% of the diameter. Providing relativelywide suction channels 1180 may help improve suction, but may lead toaccelerated wear of the back-up pad and/or an unwanted degree of flexingof the back-up pad. It may also allow portions of the abrasive sheet1110 to longitudinally deform or deflect into the channel 1180 duringuse. Providing a relatively narrow channel 1180 may provide a differentdegree of suction performance, but may help extend back-up pad life andmay help limit longitudinal deformation of the abrasive sheet 1110.

Optionally, the first and second channel edges 1194, 1198 can beconcentric and centered about the central axis 1154.

The channel width 1200 can also be selected so that it is equal to orwider than the suction holes 1184 in the abrasive sheet 1110. Thesuction holes 1184 can have diameters between about 1 mm and about 60mm, and preferably between about 8 mm and about 25 mm. Thisconfiguration may help ensure that substantially the entire crosssection of each suction hole 1184 in the abrasive sheet overlies theopen suction channel 1180. Optionally selecting the channel width 1200to be larger than the suction holes 1184 may help facilitate alignmentof suction holes 1184 with the channel 1180 even if the abrasive sheet1110 is slightly laterally misaligned with the back-up pad 1114, and mayfacilitate air flow through the suction holes and into the suctionchannel.

In the illustrated example, the back-up pad 1114 is round and thesuction channel 1180 is generally circular as viewed from the abrasivemounting face 1108. Alternatively, the suction channel 1180 can be ofanother suitable configuration that underlies some or all of the platesuction apertures 1178 and/or overlies some or all of the suction holes1184 in the abrasive sheet 1110, including, for example, rectangular,oval, and polygonal.

Optionally, the suction channel 1180 can be in simultaneous air flowcommunication with all of the plate suction apertures 1178 and all ofthe suction holes 1184. Preferably, the suction channel 1180 comprises acontinuous, closed loop channel that is generally free fromobstructions. This may facilitate air flow communication with all of theapertures 1178 and holes 1184. This configuration may help facilitateair flow within the channel 1180. Facilitating air flow within thechannel 1180 may help ensure a generally equal distribution of suctionamongst the suction holes 1184. A circular configuration may also helpensure that the suction holes 1184 will be aligned with the open face ofthe channel 1180 in any rotational position of the abrasive sheet 1110.

Alternatively, the suction channel 1180 may include two or more separatesuction channels, separated by a dividing wall or other obstacle. Insuch a configuration, each suction channel may be in fluid communicationwith only a portion of the plate suction apertures 1178 and suctionholes 1184. For example, if the open channel underlies only some of theplate suction apertures 1178 and/or overlies only some of the suctionholes 1184 in the abrasive sheet 1110, then 2 or more open channels maybe provided.

Optionally, the suction channel 1180 can be configured so that itextends through only a portion of the back-up pad 1114. In such aconfiguration, the channel endwall 1190 can be positioned longitudinallyintermediate the second pad face 1122 and the first pad face 1120. Thisconfiguration may help maintain the strength of the back-up pad 1114while still allowing sufficient suction air flow.

Alternatively, referring to FIGS. 8 and 9, the suction channel 1180 canextend through the back-up pad 1114, from the abrasive mounting face1108 to the first pad face 1120. In this configuration the channelendwall 1190 can be provided by a portion of the back-up plate 1112, forexample a portion of the pad attachment face 1118 or internal portion ofthe back-up plate 1112.

Optionally, the number of plate suction apertures 1178 can be differentthan the number of suction holes 1184 in the abrasive sheet 1110. Forexample, the suction channel 1180 may be in fluid communication witheight suction holes 1184 in an abrasive sheet 1110, and only four platesuction apertures 1178. Alternatively, a back-up apparatus 1104 mayinclude more plate suction apertures 1178 than abrasive sheet suctionholes 1184. This configuration may allow a single back-up apparatus 1104to be used with a variety of differently configured abrasive sheets1110.

Optionally, the total suction surface area of the plate suctionapertures 1178 (i.e. the area in the suction flow direction) can bedifferent than the total suction surface area of the suction holes 1184.This may be achieved, for example, by providing different numbers ofapertures 1178 and holes 1184 of generally equal size, by providing anequal number of apertures 1178 and holes 1184 of different sizes and anycombination thereof. Providing different suction surface areas mayfacilitate providing different air flow velocities at the apertures 1178and holes 1184 for a given suction air flow rate.

The suction channel 1180 can be formed in the back-up apparatus 1104using any suitable method, including, for example, routing, milling,machining, molding and stamping.

Optionally, a back-up pad can include more than one open suctionchannel. For example, a back-up pad may include two or more discretesuction channels (for example a pair of concentric suction channelsdisposed on different radii). In this configuration, the back-up platemay include two sets of suction plate apertures, one set in fluidcommunication with each suction channel. This configuration may be usedwith abrasive sheets having two sets of suction holes, arranged ondifferent radii.

Back-up Apparatus with Internal Suction Conduits

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, a back-up apparatus can be provided with one or moreinternal air suction conduits configured to connect at least one suctionopening in an abrasive sheet in fluid communication with a source ofsuction. The internal suction conduits can extend through the interiorof the back-up apparatus, and can connect suction apertures in the outerface of the back-up pad with suction apertures in the back-up plate.Optionally, the apertures in the outer face back-up pad can be radiallyoutboard of the suction apertures in the back-up plate and the internalsuction conduits can extend therebetween in a generally radialdirection. If the back-up apparatus is used in rotary applications, forexample grinding, it can be desirable to position the back-up padsuction apertures toward the edge of the back-up pad. This configurationmay help capture dust and debris that is directed toward the edge of thespinning back-up apparatus.

In a particularly preferred embodiment, an internal channel is utilizedin combination with one or more open channels. Providing internalsuction conduits may facilitate suction of debris through the back-upapparatus.

In some instances, it may be desirable to use a common suction apparatusin combination with multiple, differently sized and/or configuredback-up apparatuses. In such instances, it may be desirable to configurethe back-up apparatuses to have their suction outlets (e.g. platesuction apertures) in a generally similar, or generally the sameconfiguration that is compatible with the configuration of the suctionapparatus inlet. Internal suction conduits that extend in the generallyradial direction may be used to fluidly connect a variety of differentlysized and positioned back-up pad suction apertures (for exampleapertures that are radially outboard the sidewalls of the suctionhousing) to plate suction apertures that are positioned in a desired,standardized configuration (for example radially inboard of the suctionhousing sidewall).

Optionally, the back-up apparatus can also include an internal suctionplenum that is in airflow communication with some or all of the internalsuction conduits. The suction plenum can also be in air flowcommunication with the back-up pad suction apertures and back-up platesuction apertures. Providing a suction plenum may help equalize thesuction in each of the internal conduits.

Referring to FIGS. 10 and 11 a back-up apparatus 2104 includes a back-upplate 2112, a back-up pad 2114 and an interface layer 2124. The back-upapparatus 2104 may be generally similar to the back-up apparatuses 104,1104, and like features are illustrated using like reference numeralsstarting at 2100. The back-up apparatus 2104 may have a larger diameterthan the back-up apparatus 1104.

In this example, the back-up plate 2112 includes a plurality of platesuction apertures 2178. The plate suction apertures 2178 are positionedabout the central axis 2154, at a radial distance 2204. The radialdistance 2204 can be set so that the plate suction apertures 2178 areradially inboard of the housing sidewall 2160 (shown in phantom in FIG.11) whereby the plate suction apertures 2178 are in air flowcommunication with the suction housing inlet.

The back-up pad 2114 includes a circular open suction channel 2180 opento the abrasive mounting face 2108. The suction channel 2180 is locatedtoward the centre of the back-up pad 2104.

In the illustrated example, suction channel 2180 is radially inboard ofthe suction housing sidewall 2160. Alternatively, the suction channelcan be positioned radially outboard of the suction housing sidewall 2160and can be connected to the back-up plate suction apertures 2178 usingsuction conduits, for example, as described below. Positioning thesuction channel outside the perimeter of the suction housing 2156 canhelp facilitate providing suction toward the periphery of the back-uppad 2114, while using a relatively smaller (radially) suction housing2156.

In the example illustrated, a plurality of interior suction conduits2206 are provided in the back-up pad 2114 to provide fluid communicationbetween the plate suction apertures 2178, disposed within perimeter ofthe housing sidewall 2160, and a plurality of pad suction apertures2208. The pad suction apertures 2208 can be located toward the edge ofthe back-up apparatus 1104 (which may help improve suction performance)and may be disposed outside the perimeter of the sidewall 2160.

The suction conduits 2206 are generally enclosed passageways extendingwithin the back-up apparatus. In the illustrated embodiment, theconduits 2206 have a generally rectangular cross section with a firstconduit endwall 2210, an opposed second conduit endwall 2212 and opposedconduit sidewalls 2214 extending therebetween. Alternatively, thesuction conduits 2206 may have any other suitable cross section (forexample a circular conduit) and may have a different number of walls.The cross sectional area of the conduits (taken in the direction ofsuction air flow) can be selected based on the desired suction air flow,the performance of the suction source, the number of conduits in theback-up apparatus, the size of the back-up pad and other factors. Thecross-sectional area of each conduit can be between about 1 mm2 andabout 500 mm2, and preferably is between about 10 mm2 and about 100 mm2.

The suction conduits 2206 can extend in the generally radial direction,for example in a direction that is parallel to the plane containing theabrasive mounting face 2108. In the illustrated example, the internalsuction conduits 2206 extend radially across the housing sidewall 2160.

Optionally, the conduits 2206 can be generally straight or linearconduits extending transversely through the back-up pad in the radialdirection. Alternatively, the suction conduits 2206 can be arranged atan angle, relative to the radial direction, or may be curved (forexample within a plane parallel to the abrasive mounting face 2180, in aplane that is not parallel to the abrasive mounting face 2180 and anycombination thereof.

Providing the suction conduits at an angle relative to the radialdirection may allow the movement of the back-up apparatus to help urgesanding debris along the suction conduits 2206, to the plate suctionapertures 2178.

Suction conduits arranged at an angle relative to the radial direction,but still fluidly connecting a suction inlet (e.g. for example a padsuction aperture 2208) at a first radial distance with a suction outlet(e.g. plate suction apertures 2178) at a second, smaller radial distancecan be considered to be extending at least partially in the generallyradial direction.

Optionally, the number of suction conduits 2206 can correspond to thenumber of plate suction apertures 2178. Alternatively, the number ofsuction conduits 2206 can be different than the number of plate suctionapertures 2178.

Optionally, the back-up apparatus can be configured to include only adiscrete plurality of pad suction apertures, instead of also includingan open suction channel. In such a configuration, each of the padsuction apertures can be fluidly connected to the suction source usingthe internal suction conduits.

In some applications, forming a continuous, open suction channel in theback-up pad may be undesirable. For example, in rotary sandingapplications, a peripheral suction channel may weaken the structuralintegrity of the back-up pad and may contribute to accelerated orpremature back-up pad replacement or failure. In such applications, itmay be desirable to remove a relatively smaller amount of material fromthe periphery of the back-up pad, while still providing suction inletapertures toward the edges of the back-up pad. The amount of materialrequired to provide a desired level of back-up pad integrity can dependon, for example, the type of material used, and the expected operatingconditions of the back-up pad. In such applications, it can beadvantageous to provide an internal suction passage that can connect theplurality of suction apertures to a common suction source. Preferably,the internal suction passage can include a common channel or plenum thatis in fluid communication with multiple suction apertures. This may helpmaintain a generally equal level of suction at each suction aperture.

Referring to FIGS. 12-14, another example of a back-up apparatus 3104includes a back-up plate 3112, a back-up pad 3114, interface layer 3124(optionally adhesive or mechanical attachment means). The back-upapparatus 3104 may be generally similar to back-up apparatuses 104,1104, 2104 and like elements are identified using like referencenumerals starting at 3100. The back-up apparatus 3104 is rotatable aboutthe central axis 3154 and the back-up apparatus 3104 includes a suctionpassage that extends from suction inlets on the back-up pad, to theplate suction apertures and into the suction housing.

In this example, the back-up plate 3112 includes a plurality of platesuction apertures 3178 extending through the back-up plate 3112. Theplate suction apertures 3178 are located at a first radial distance 3204from the central axis 3154. The first radial distance 3204 can beselected so that plate suction apertures 3178 are positioned within thesuction housing 3156 (e.g. radially inboard of the housing sidewall3160—shown in phantom). For example, the first radial distance can bebetween about 5 mm and about 500 mm, and preferably can be between about10 mm and about 100 mm. The suction housing can be of any compatiblesize so that the suction housing sidewall surrounds the plate suctionapertures.

Optionally, the radial position of the plate suction apertures 3178 canbe about the same for a variety of back-up apparatus 3104 sizes. Forexample, the radial distance 3204 can be the same for 4 inch, 6 inch and8 inch diameter back-up apparatuses 3104. In this configuration, thesame suction housing 3156 can be used in combination with a variety ofback-up apparatus diameters. This may allow a single suction housing3156 to be used with a variety of different back-up apparatus 3104.

In the illustrated example, the back-up pad 3114 is a multi-layerback-up pad having an inner layer 3210 (adjacent the back-up plate 3112and comprising the first pad face 3120), an outer layer 3212 (adjacentthe interface layer 3214 and comprising the second pad face 3122) and anintermediate layer 3214 positioned therebetween. The layers arepermanently affixed to each other using a suitable adhesive. The layers3210, 3212 and 3214 can be made of the same, or different materials.

The inner layer 3210 comprises a plurality of inner pad suctionapertures 3216 that can be registered with the plate suction apertures3178. The inner layer 3210 can be permanently and non-rotatably bondedto the back-up plate 3112. This configuration may help ensure the innerpad suction apertures 3216 remain registered with the plate suctionapertures 3178 during use.

The inner pad suction apertures 3216 can be arranged in any pattern thatcompliments the arrangement of the plate suction apertures 3178. In theillustrated example, the inner pad suction apertures 3216 are positionedalong a constant circumference, and at a radial distance 3218 from thecentral axis 3154. The radial distance 3218 is generally equal to theradial distance 3204 of the plate suction apertures 3178. Alternatively,the apertures 3216 and 3178 need not be provided on a constantcircumference. Because the back-up pad 3114 can be attached to theback-up plate 3112 during manufacture of the back-up apparatus 3104, itsrotational alignment can be carefully, and a user need not work

The outer layer 3212 includes a plurality of outer pad suction apertures3220. In the illustrated example, the outer pad suction apertures 3220are positioned around the periphery of the outer layer 3212, at a radialdistance 3222 from the central axis 3154. The radial distance 3222 isgreater than the radial distance 3218. Optionally, the radial distance3222 can be selected so that the plurality of outer pad suctionapertures 3220 are radially outboard of the suction housing sidewall3160. In this example, the plurality of outer pad suction apertures 3220form the back-up pad suction inlets. Alternatively, the outer padsuction apertures 3220 can be positioned in a different pattern and at adifferent location on the outer layer 3212.

A plurality of connecting webs 3224 are provided between adjacent outerpad suction apertures 3220. The number and spacing of outer layersuction apertures 3220 can be selected to provide a desired number andsize of connecting webs 3224. This may help facilitate providing aback-up pad 3114 with suction and sufficient pad integrity. The numberand spacing of the pad suction apertures 3220 can also be selected tohelp minimize debris escaping from the edge of the back-up apparatus3104. For example, spacing the pad suction apertures 3220 relatively farapart from each other may help increase the strength of the back-up pad3114, but may allow some dust or debris to escape by passing betweenadjacent pad suction apertures 3220. Alternatively, placing the padsuction apertures 3220 relatively close together may help prevent debrisfrom escaping between the pad suction apertures 3220, but may weaken theback-up pad 3114. For a given surface treating operation, theconfiguration of the pad suction apertures 3220 can be selected toappropriately balance suction coverage and back-up pad strength (whetherused alone or in combination with other suction passages, channels andconduits).

Optionally, the number of outer layer suction apertures 3220 can bedifferent than the number of inner layer suction apertures 3216. Forexample, an 8 inch back-up pad may include 14 outer layer suctionapertures and 8 inner layer suction apertures.

The intermediate layer 3214 can include a plurality of internal suctionconduits 3206 fluidly connecting the outer pad suction apertures 3220with the inner pad suction apertures 3216.

In the illustrated example, the plurality of internal suction conduits3206 are fluidly connected to an internal plenum 3224, which is in fluidcommunication with the inner pad suction apertures 3216.

In the illustrated example, the intermediate layer 3214 is a two piecelayer including a generally annular ring member 3226 surrounding agenerally circular central member 3228. Alternatively, the intermediatelayer 3214 can be a unitary member or can include a different number ofdiscrete members.

In the illustrated example the ring member 2226 includes a plurality ofradial slots 3330, generally extending in a direction parallel to theplane containing the abrasive mounting face 3108. The distal ends 3332of the slots 3330 are registered with and in air flow communication withthe outer pad suction apertures 3220. When sandwiched between the innerand outer pad layers 3210, 3212, the sidewalls 3334 of the slots 3330and portions of the inner and outer pad layers 3210, 3212 co-operate toprovide the sidewalls and endwalls that define the internal suctionconduits 3206. Also when sandwiched between the inner and outer padlayers 3210, 3212, the generally annular gap between the ring member3226 and the central member 3228 defines a generally annular internalplenum 3224, which is open to the proximal ends 3336 of the internalsuction channels 3206.

The central member 3228 may help provide strength to the back-up pad3114, for example to help resist the axial compressive forces applied bya central safety fastener, as explained below. Adjusting the size of thecentral member 3228 may adjust the volume of the internal plenum 3206.

In this example, air and debris entering the outer pad suction apertures3220 can travel through the plurality of internal conduits 3206 and flowinto the internal plenum 3224. Air and debris in the internal plenum3224 can then be sucked into the suction housing 3156, via the inner padsuction apertures 3216 and plate suction apertures 3178, for removal.

Alternatively, for example in embodiments where the number of outer padsuction apertures equals the number of inner pad suction apertures,corresponding pairs of pad apertures can be directly connected usingdedicated suction conduits, without the need for an internal plenum.

The internal suction conduits 3206 and internal plenum 3224 can have anysuitable configuration, and need not be limited to radial conduitscoupled to an annular plenum.

Optionally, a back-up pad can include any suitable combination ofsuction channels, suction conduits and suction apertures. For example,referring again to FIGS. 10 and 11, the back-up pad 2114 includes aplurality of pad suction apertures 2208 positioned at a first radialdistance 2238 around the periphery of the back-up pad 2114, and an opensuction channel 2180 positioned inboard of the plurality suctionapertures 2208, at a second radial distance 2186.

In this configuration, the plurality of suction apertures 2208 locatedaround the periphery of the back-up pad 2114 are not through-holes.Instead, the plurality of suction apertures 2208 are fluidly connectedto the open suction channel 2180 (and therefore the plate suctionapertures 2178) by the plurality of internal suction conduits 2206. Inthe illustrated example, the number of pad suction apertures 2208 is thesame as the number of plate suction apertures 2178.

Referring to FIG. 10, an abrasive sheet 2110 suitable for use with theback-up pad 2114 includes two sets of suction holes 2184. One set ofsuction holes is arranged to align with the plurality of pad suctionapertures 2208. The other set of suction holes is arranged to overliethe open suction channel 2180.

In this example, the back-up pad 2114 suction inlet includes acombination of the plurality of suction apertures 2208 and the opensuction channel 2180.

Configuration of a Safety Fastener

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, a safety fastener can be used to secure an abrasive sheetto a surface treatment apparatus. Under certain operating conditions,for example high temperatures and/or high friction between the abrasivesheet and the surface being treated, there can be a risk that theabrasive sheet can separate from the back-up pad. For example, theprimary attachment mechanism used to hold the abrasive sheet to theback-up apparatus, for example hook and loop fasteners and someconventional adhesives, can weaken over time, reducing the strength ofthe bond with the abrasive sheet. In some applications, it can beadvantageous to provide a secondary, safety fastening mechanism tosecure the abrasive sheet to the back-up pad. The safety fasteningmechanism can be configured to keep the abrasive sheet attached to thesurface treating apparatus in the event of a primary attachmentmechanism failure.

Preferably, the safety fastening mechanism is releasable to facilitatechanging and replacement of the abrasive sheets, and is re-usable. Theback-up apparatus can be configured to receive the safety fasteningmechanism.

Referring to FIGS. 15 and 16, a rotary sanding apparatus 4100 includesrotary driving apparatus 4102 and a rotatable back-up apparatus 4104.The sanding apparatus 4100 may be generally similar to the sandingapparatuses 100, 1100, 2100 and 3100, and like features are illustratedusing like reference numerals starting at 4100. The back-up apparatus4104 is rotatable about a central axis 4154.

Under some circumstances, an abrasive sheet can unintentionally becomeseparated from a back-up apparatus while the sanding apparatus is inuse, for example due to a failure of the bond between the abrasive sheetand the abrasive mounting face. Such separations may cause damage to thesurface being sanded, and may pose a safety risk to users. For example,if the back-up apparatus is operating at a relatively high speed (forexample between about 2500-15000 rpm), an abrasive sheet that isseparated from the back-up apparatus may fly off of the sandingapparatus, possibly striking a user or bystander. It may be desirable touse a safety fastening mechanism to help prevent separation of theabrasive sheet 4110 from the sanding apparatus 4100.

Referring again to FIGS. 15 and 16, the sanding apparatus 4100 includesa safety fastener 4240. The safety fastener 4240 provides an additionalmeans for securing the abrasive sheet 4110 to the sanding apparatus4100, and may serve as a secondary or back-up attachment means in theevent that the bond between the abrasive sheet 4110 and the abrasivemounting face 4108 should fail.

In the illustrated embodiment, the safety fastener includes 4240 asafety bolt 4242 that extends through the abrasive sheet 4110 and intothe back-up apparatus 4104. Alternatively, any suitable fastener can beused, including, for example a screw, a locking pin, and a clampingmechanism.

In this example, the back-up plate 4112 includes a central bore 4244 forreceiving the safety bolt 4242. The back-up pad 4114 includes centralopening 4246 that is in registration with the central bore 4244 on theback-up plate 4112. The safety bolt 4242 is releasably securable withinthe central bore 4244 and is configured to extend through both thecentral opening 4246 in the back-up pad 4114 and a central opening 4248in the abrasive sheet 4110. When the safety bolt 4242 is secured in thecentral bore 4244, the abrasive sheet 4110 is secured to the back-upapparatus 4104. The safety bolt 4242 includes an attachment portion 4250(for example the shaft of the bolt) and a retaining portion 2452 (forexample the head of the bolt). The bolt 4242 and bore 4244 can have anycomplimentary cross-sectional shapes. It will be appreciated that if thecentral bore is not recessed, then the safety fastener may not need toextend through the back-up pad.

In the illustrated example, the central bore 4244 is internally threadedand the safety bolt can be screwed into the bore 4244. Thisconfiguration may help facilitate the insertion of the safety bolt 4242to secure an abrasive sheet 4110, and the subsequent removal of thesafety bolt 4242 to facilitate replacement of the abrasive sheet 4110.Alternatively, the safety fastener can be secured to the apparatus 4100using another suitable method, including, for example, locking pins,detent members, an interference fit and magnetic fasteners.

Optionally, the threads in the central bore can be integral with theback-up plate 4112, or secured thereto such as by welding, an adhesive,mechanical fasteners or the like or provided by a separate anchor memberthat is provided in the back-up apparatus 4104.

In the illustrated example, the back-up plate is a molded plastic platethat includes a metal anchor member 4254, which is molded into the plate4112. The anchor member 4254 is a metal nut having threads that arecompatible with the threads on the safety bolt 4242. Providing a metalanchor member 4254 in the back-up plate 4112 may help increase thestrength of the threads in the central bore 4244 (as opposed to moldedplastic threads).

Optionally, the central bore 4244 may be a through hole in the back-upplate 4114. In this configuration, the central bore 4244 may provideaccess to the drive spindle 4256 on the driving apparatus 4102.Optionally, the drive spindle 4256 can include a spindle bore 4258 thatis sized to receive the safety bolt 4242. Preferably, the spindle bore4258 is internally threaded, and the safety bolt 4242 can be threadedinto the spindle bore 4258. Threading the safety bolt 4242 into thespindle bore 4258 may allow the safety bolt 4258 to fasten the abrasivesheet 4110 to the driving apparatus 4102. Optionally, the safety bolt4258 can be secured only to the spindle bore 4258, and need not engagethe central bore 4244. For example, the central bore 4244 can be asmooth through hole and the safety bolt 4258 (or other type of fastener)can extend freely thought the central bore 4244 and be retained byengagement (threaded or otherwise) with the spindle bore 4258. This maystill help prevent separation of the abrasive sheet 4110 from theback-up apparatus 4104.

An abrasive sheet 4110 that is compatible with the safety bolt 4242 canhave a central fastener aperture 4248 for receiving the safety bolt4242. The abrasive sheet 4110 includes both an attachment face forcoupling the abrasive sheet 4110 to the abrasive mounting face 4108 ofthe back-up pad 4114 (as described above), and an attachment aperture4248 for receiving a safety fastener 4240 for coupling the abrasivesheet 4110 directly to the back-up plate 4112 and/or the drivingapparatus 4102.

The central fastener aperture 4248 can be at least partially registeredwith the central bore 4244 when the abrasive sheet 4110 is in place.Preferably, the central fastener aperture 4248 has a diameter that issmaller than the diameter of the retaining portion 4252 of the safetybolt 4242.

Optionally, the retaining portion can 4252 include a washer 4260 that isrotatable relative to the safety bolt 4242 and is non-rotatable withrespect to the back-up pad as the safety bolt is installed. The washer4260 is sized to be freely rotatable relative to the safety bolt 4242.In the illustrated example, the central opening in the washer 4260 isslightly larger than the diameter of the shank of the safety bolt 4242.When the retaining portion 4252 of the bolt 4242 is spaced apart fromthe abrasive sheet, the washer 4260 is free to rotate. As the bolt 4242is tightened, the retaining portion 4252 and the washer 4260 approachthe abrasive sheet 4110 until the washer 4260 makes contact with theabrasive sheet 4110. In this position, the friction between the washer4260 and the abrasive sheet is sufficient to inhibit free rotation ofthe washer 4260. The bolt 4242 can continue to be tightened, as it canrotate relative to the washer 4260. As the bolt 4242 is tightened, thefriction between the washer 4260 and the abrasive sheet 4110 canincrease, as the retaining portion 4252 contacts and rotates relative tothe outer face of the washer 4260. When the bolt 4242 is fullytightened, the compressive forces exerted by the safety bolt 4242 on thewasher 4260 and abrasive sheet 4110 inhibit rotation of the washer 4260relative to the abrasive sheet 4110 when the abrasive sheet 4110 is inuse. During this mounting operation the retaining portion 4252 of thebolt 4242 need not contact the abrasive surface. Also, the washer 4260need not rotate relative to the abrasive sheet 4110 while it is incontact with the abrasive sheet 4110.

In the absence of the washer 4260, when the safety bolt 4242 is beinginstalled and removed (i.e. rotated relative to the abrasive sheet4110), the underside of the head of the safety bolt 4242 would grindagainst the abrasive material on the abrasive sheet 4110. This grindingmay wear the safety bolt 4242 and eventually lead to a failure. When thewasher 4260 is provided on the safety bolt 4242, the washer can contactthe abrasive material and remain stationary relative to the abrasivematerial as the safety bolt 4242 is tightened and loosened. When thesafety bolt 4242 has been fully tightened, there is no longer relativerotation between the safety bolt 4242 and washer 4260, and both thesafety bolt 4242 and the washer 4260 can move in unison with the back-upapparatus 4104.

Optionally, the back-up pad 4114 is configured such that when thefastener 4240 is fully secured within the central bore 4244, the head ofthe safety bolt 4242 is recessed at or below the abrasive mountingsurface 4108 of the pad 4114. For example, the back-up pad 4114 may havea recess to accommodate the head of the safety bolt 4242, and/or may besufficiently compressible such that the back-up pad 4114 can compress asthe safety bolt 4242 is tightened. This configuration may help preventthe head of the safety bolt 4242 from contacting the surface beingsanded.

Configuration of a Mounting Tool

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, a mounting tool can be used to place an abrasive sheet ona corresponding back-up apparatus. Obtaining proper radial androtational alignment between an abrasive sheet and a back-up apparatuscan be challenging when the abrasive sheet is attached by hand. It canbe advantageous to properly align the abrasive sheet on the back-upapparatus. Improper radial or lateral alignment can cause imbalances andvibrations when the surface treatment apparatus is use. Improperrotational alignment can result in improper registration of the suctionholes in the abrasive sheet with the suction apertures in the back-uppad, which may impede suction performance. Placing the abrasive sheet onthe back-up apparatus may be particularly challenging when the suctionapparatus is active, as the suction from the pad suction apertures maytend to pull the abrasive sheet against the back-up pad before it can beproperly aligned.

It may be advantageous to provide a mounting tool that can be used toassist a user when attaching an abrasive sheet to a back-up pad,particularly when the abrasive sheet includes suction holes. It may bedesirable to have a mounting tool that can be used when the suctionapparatus is active.

For example, in instances when the back-up pad includes a plurality ofdiscrete pad suction apertures in the abrasive mounting face (instead ofor in addition to an open suction channel), it may be advantageous touse an abrasive sheet mounting tool to help facilitate placement of anabrasive sheet on the back-up pad. Alternatively, if the back-up padincludes an open suction channel, the mounting tool can be configured sothat it is compatible with the open suction channel.

Referring to FIGS. 17 and 18, an abrasive sheet mounting tool 5262includes a body 5264 and a plurality of alignment pins 5266. The body5264 includes a handle portion 5268 for allowing a user to carry andmanipulate the tool 5262.

Referring also to FIG. 19, as exemplified, the mounting tool 5262 isconfigured to be used in combination with a back-up apparatus 6104having a plurality of pad suction apertures 6208 and an abrasive sheet6110 having a corresponding plurality of suction holes 6184. The padsuction apertures 6208 and suction holes 6184 in the abrasive sheet 6110are arranged in a complimentary pattern so that the suction holes 6184can be registered with the pad suction apertures 6208, as explained indetail herein.

The plurality of alignment pins 5266 extend from the body 5264. In theillustrated example the mounting tool 5262 includes three alignment pins5266. In other examples, the mounting tool 5262 may include a differentnumber of alignment pins, including for example two, four or morealignment pins.

The mounting tool 5262 preferably has a central tool axis 5268. Thealignment pins 5266 can be radially spaced apart from the tool axis by aradial distance 5272. In the illustrated example, the alignment pins5266 are spaced and arranged in a pattern that corresponds to thepattern of suction holes 6184 and pad suction apertures 6208. In thisconfiguration each one of the plurality of alignment pins 5266 can bealigned with a corresponding one of the plurality of suction holes 6184in the abrasive sheet 6110 so that the abrasive sheet 6110 can be slidonto, and supported by the mounting tool 5262 (FIG. 18).

With an abrasive sheet 6110 supported on the mounting tool 5262, theuser can then align the mounting pins 5266 with respective ones of thepad suction apertures 6208 (or one or more open channels), and slide atleast a portion of the alignment pins 5266 into the apertures 6208 (orthe open channel or channels). In this position, the abrasive sheet 6110is both radially and rotationally aligned with the back-up pad 6114, sothat the abrasive sheet 6110 is generally centred relative to theback-up pad 6114 and the suction holes 6184 in the abrasive sheet 6110are registered with the pad suction apertures 6208 (FIG. 19).

From this aligned position, the abrasive sheet 6110 can be slid down thealignment pins 5266 (in the longitudinal direction), toward the back-uppad 6114. The abrasive sheet 6110 can then be pushed into contact withand can be coupled to the abrasive mounting face 6108. The abrasivemounting face 6108 can include any suitable fastening system, including,for example, adhesive and mechanical interface layers described herein.

Optionally, the tips of the alignment pins 5266 can be contoured (e.g.,rounded). Rounding, or otherwise shaping the tips of the alignment pins5266 may help facilitate insertion of the alignment pins 5266 into thesuction holes 6184 and pad suction apertures 6208. The cross-sectionalshape of the alignment pins 5266 can be any suitable shape that can fitwithin the suction holes 6184 and pad suction apertures 6208, including,for example, circular (as illustrated) and polygonal.

Optionally, alignment pins 5266 may be moveably mounted on the tool. Forexample, they may slidably mounted thereto or removably attached theretoso that the alignment pins 5266 may be moved to alternate positions.Referring again to FIG. 17, in the example illustrated, the alignmentpins 5266 are removably attached. As exemplified, the mounting tool 5262includes a generally planar pin support pad 5274 mounted on thesupporting body 5264. In this configuration, the handle portion 5268includes a rod-like handle member 5276 extending from the back of thesupporting body 5264. Optionally, the planar support pad 5274 can havethe same configuration as the back-up pad 5114.

The pin support pad 5274 can include a plurality of pin apertures 5278that can be sized to receive the mounting pins 5266. Optionally, themounting pins 5266 can be releasably received within the pin apertures5278, so that the mounting pins 5266 can be removed from the pinapertures 5278 and re-inserted into any one of the pin apertures 5278.

The mounting pins 5266 can be held in the pin apertures 5278 by aninterference fit, or by any other suitable fastening mechanism,including, for example, adhesives and mechanical fasteners. In theillustrated example, the alignment pins 5266 are held in position usingscrews 5280 that extend through the supporting body 5264.

Optionally, the pin support pad 5274 can be detachable from thesupporting body 5264. In this configuration, the pin support pad 5264can be replaced with a different pin support pad that is configuredmatch a different suction hole/pad suction aperture pattern. Thealignment pins 5266 can then be mounted in the new pin support pad suchthat they are aligned with the new suction hole pattern. This may allowthe supporting body 5264 to be used in combination with a plurality ofdifferent abrasive sheet/back-up pad configurations.

Alternatively, or in addition, a single pin support pad 5274 can includea plurality of sets of mounting pin apertures 5278 (see additionalapertures 5278 a shown in phantom in FIG. 17), each set can beconfigured to match a given suction hole/pad suction aperture pattern.The alignment pins 5266 can be positioned in different ones of the setsof mounting pin apertures 5278, based on, for example, the specificback-up pad being used for the current job. This configuration may helpfacilitate mounting a variety of differently configured abrasive sheetson a corresponding plurality of back-up pads using the same pin supportpad.

Referring to FIGS. 20-22, another example of a pin mounting tool 7262includes three alignment pins 7266 mounted on a supporting body 7264. Inthis configuration the supporting body 7264 includes a generallyT-shaped frame 7282, and the handle portion 7268 includes a gripableregion 7284 on the frame.

The mounting tool 7262 does not include a pin mounting pad, or anaxially extending handle member projecting from the supporting body. Inthis example, the frame 7282 is configured so that the alignment pins7266 are located an appropriate radial distance 7272 from the centraltool axis 7270, so that the alignment pins 7266 can be aligned with thesuction holes 6184 and pad suction apertures 6208 in a given abrasivesheet 6110 and back-up pad 6114, respectively.

The mounting tool 7262 can also be re-configurable to accommodatedifferent suction hole patterns. For example, frame 7282 can includemultiple alignment pin attachment locations 7278, 7278 a so that theposition of the alignment pins 7266 can be changed as needed.

The mounting tool 7262 may also be used to mount abrasive sheets thatare secured to a back-up apparatus using a central locking fastener.Examples of such abrasive sheets include fiber discs and a heavy 24 or36 grit resin cloth sheets. These abrasive sheets can include a centralaperture 6248 that can be registered with the spindle of a drivingapparatus, such as an electric grinder. A locking nut (for example a nutsimilar to nut 10290 a described below) can be inserted into theaperture 6248 and threaded onto the spindle. When mounting the abrasivesheet 6110, the spindle can be locked so it cannot turn freely. Theheavy abrasive sheets can be slid onto the alignment pins 7266 and thepins 7266 can be placed into corresponding pad suction apertures (orinto a suitable open suction channel). This may help align the suctionholes in the abrasive sheet with the pad suction apertures (or suctionchannel), and may help register the central aperture 6248 with thespindle.

Mounting tool 7262 does not include a pin support pad. The absence of apin support pad extending laterally between the alignment pins 7266 mayhelp provide sufficient working space for a user to access the centralaperture 6248 while the abrasive sheet 6110 is supported on the mountingtool 7262, for example to insert and tighten a locking nut to secure theabrasive sheet to the back-up apparatus. Optionally, the mounting pins7266 can be left in the pad suction apertures (or suction channel) whilethe fastening nut is installed. Optionally, the alignment pins 7266 canbe used to help impede rotation of the abrasive sheet relative to theback-up apparatus while the locking nut is being tightened, oroptionally loosened. This may help keep all the suction holes lined upwith the pad suction apertures (or suction channel) while tightening nutand securing the abrasive sheet to the back-up apparatus. If the lockingnut has been tightened too much, for example if it tightens during use,the spindle can again be locked and the alignment pins can bere-inserted in the pad suction apertures to help unscrew the lockingnut.

The mounting tools and alignment pins can be made from any suitablematerials, including, for example plastic and metal. The mounting toolscan be used with any suitable type of back-up pad, including, forexample, rotary back-up pads and double-action back-up pads.

Configuration of a Back-Up Plate

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, a back-up apparatus can include a back-up plate that isgenerally planar. Optionally, the back-up plate can be free fromintegrated hardware. Conventional back-up plates tend to have 3D, ornon-planar configurations, and are formed from injection molded plastic.Mounting hardware is often molding into the part. The rear surfaces ofconventional back-up plates can vary from plate to plate, and betweensizes of back-up apparatus. The differences in the configuration of theback-up plates can make it difficult to provide an apparatus that iscompatible with multiple styles and sizes of back-up apparatus,optionally for different purposes.

Injection molding back-up plates can be relatively expensive. Designchanges to molded back-up plates can require changes to thecorresponding molds, dies etc. Forming back-up plates from a planarsheet of material can be relatively lower cost than injection molding,and can allow for increased design flexibility.

In the examples describe previously, the back-up plate is generally morerigid than the back-up pad. Optionally, the back-up plate can be formedfrom molded plastic. In such a configuration, the back-up plate may havea curved, three-dimensional rear face (facing away from the back-uppad).

Alternatively, according to this aspect, the back-up plate can be agenerally planar member, having a generally planar, or two-dimensional,rear face. Providing a planar rear face may help reduce the amount ofmaterial required to form the back-up plate.

Providing a planar rear face may also help standardize the axialdimensions/configurations of different sized back-up plates.Standardizing the size and shape of the rear face may help facilitatethe use of the same auxiliary equipment, such as the suction housing,with a variety of back-up plates of different sizes. This configurationmay allow a user to quickly change the back-up apparatus on a sandingapparatus (for example from an eight inch grinding abrasive to a sixinch sanding abrasive) without having to adjust or reconfigure thesuction housing, and optionally other equipment.

Planar back-up plates may also be easier and/or less expensive tomanufacture than an analogous mold plastic back-up plate. The materialused in the planar back-up plate can be selected that it is more warpresistant than conventional molded back-up plates. The back-up plate canbe formed in any suitable shape for use with a variety of surfacetreating apparatuses, and need not be limited to circular or disc-likeplates.

Referring to FIGS. 23 and 24, an example of a back-up apparatus 9104includes a generally planar back-up plate 9112, a back-up pad 9114 andan interface layer 9124. The back-up apparatus may be generally similarto the back-up apparatus 1104, 2104, etc. and like features areidentified using like reference numerals, starting at 9104.

The planar back-up plate 9112 has a planar pad attachment face 9118 anda parallel, opposed planar rear face 9116. The planar back-up plate 9112is adapted to be mounted to a driving apparatus. For example, planarback-up plate 9112 may also include a central plate bore or aperture9244 sized to removably receive a mounting fastener 9290, for connectingthe back-up apparatus 9104 to a suitable driving apparatus.

The back-up pad 9114 can be any suitable back-up pad, including, forexample, any of the back-up pads described herein. In the illustratedexample, the back-up pad 9114 has a first pad face 9120, fixedlyfastened to the pad attachment face 9118, and second pad face 9122coupled to the interface layer 9124.

The interface layer 9124 includes an abrasive mounting face 9108 forsupporting an abrasive sheet 9110. The back-up pad 9114 and theinterface layer 9124 include a central pad aperture 9246 and centralinterface aperture 9288, respectively, registered with the central plateaperture 9246. The central pad aperture 9246 and interface aperture 9288co-operate to extend from the pad attachment face 9118 to the abrasivemounting face 9108. The central pad aperture 9246 and interface aperture9288 are sized to removably receive the mounting fastener 9290. In thisconfiguration, the mounting fastener 9290 (for example a mounting bolt)is not permanently coupled to, or molded into, the back-up plate 9112.Accordingly, mounting fastener 9290 can be separated from the back-upplate 9112, and the same mounting fastener 9290 can be re-used to attachmultiple back-up plates 9112.

Preferably, the planar material used to form the back-up plate isgenerally rigid, with sufficient strength to withstand the expectingoperating conditions of the sanding apparatus, including, for examplepolycarbonate, plastics, wood, metal and composite materials, preferablythermoplastic polymers and more preferably polycarbonate. The plate mayhave a thickness from about 2 mm to about 20 mm and preferably betweenabout 5 mm to about 15 mm. In the illustrated example, the planar platematerial has a tensile strength of between about 40 MPa to about 80 MPaor more and a Young's modulus of between about 1.8 GPa and about 2.5 GPaor higher. Alternatively, the plate material can have a tensile strengththat is lower than 40 MPa or higher than 80 MPa, and can have a Young'smodulus that is lower than about 1.8 GPa or higher than about 2.5 GPa.

In addition to including a central mounting aperture 9246, a pluralityof plate suction apertures 9178 can be formed in the planar back-upplate 9112. Optionally, the back-up plate 9112 can be provided withplate suction apertures, even if it is not intended to be used in asanding apparatus that includes a suction system.

For example, optionally, all of the back-up plates manufactured caninclude plate suction apertures. In this configuration, the presence ofplate suction apertures will not materially affect the performance of anon-suction back-up pad (the back-up pad material will simply cover theapertures 9178), and being equipped with plate suction apertures willenable the planar back-up plates to be used in combination with thesuction systems described herein. Manufacturing back-up plates in thismanner may allow a single configuration of back-up plate to be used withboth suction and non-suction sanding apparatuses. This may help reducethe cost of producing the back-up plates, as the configuration of theback-up plates need not be changed based on the type of back-up padused.

Referring to FIG. 25, instead of molding, the planar back-up plates 9112can be formed by forming the back-up plates 9112 from larger, planarsheets of material 9292. As used herein, forming is intended includeother analogous separating operations, including, for example, cutting,milling, drilling, stamping, routing, etc.

The method of manufacturing the planar back-up plate 9112 can includethe steps of providing a planar sheet of plate material 9292 and forminga back-up plate 9112 from the sheet of plate material 9292. The methodcan also include the steps of forming a central mounting aperture 9246in the back-up plate 9112 to accommodate a mounting fastener 9290. Theforming operation may comprise cutting, stamping and the like.

Optionally, the method includes cutting the back-up plate 9112 into acircular disc shape having a plate radius 9294. Circular back-up platesare suitable for use in combination with the sanding apparatusesdescribed herein. In other examples, the back-up plates need not becircular.

Preferably, the plate radius 9294 is selected so that it is smaller thana pad radius 9296 of a back-up pad 9114 that is to be coupled to theback-up plate 9112. Optionally, the plate radius 9294 can be betweenabout 50 and about 100% of the back-up pad radius 9296. Configuring theback-up plate 9112 to be smaller than the back-up pad 9114 may helpfacilitate axial bending and flexing of the peripheral portion of theback-up pad 9114. The difference between the plate radius 9294 and thepad radius 9296 may be selected based on the desired amount of flexingof the back-up pad 9114.

Optionally, the steps of cutting the planar back-up plate 9112, formingthe central mounting aperture 9246 and forming the plurality of platesuction apertures 9178 can be performed substantially simultaneously.This may help increase production speed. Alternatively, these steps canbe performed sequentially.

To assembly the back-up apparatus 9104, the back-up pad 9114 can beglued to the planar back-up plate 9112.

Surface Treating Apparatus with Suction System that is Compatible withFibre Discs

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, a surface treating apparatus that includes a suctionsystem can be configured to be compatible for use in grinding operationsand for use with fibre discs and other relatively aggressive abrasivemedia. The surface treating apparatus can include a back-up plate thatis configured for use with fibre discs, and the like, and need notinclude a compliant, flexible back-up pad. To facilitate suction, forexample in a manner analogous to the apparatuses described above, theback-up plate and fibre disc can include suction apertures and suctionholes, respectively. The suction apertures in the back-up plate can bethrough holes, or can be configured in any other suitable configuration,including, for example, having suction channels, conduits and plenums asdescribed herein.

Conventional fibre disc sanding apparatuses do not include back-upapparatuses of the nature described herein. The stiffness of the fibredisc abrasive sheets can be sufficient to be used in grinding operationswithout the need for an external back-up apparatus. Also, inconventional grinding applications, the fibre disc abrasive is notintended to follow the contours of a surface being grinded, and theflexibility of the back-up pads described herein may be unnecessary.

Conventional fibre disc sanding apparatuses also do not include suctionsystems of the nature describe herein. Conventional fibre discs do notinclude suction holes, and the sanding apparatuses do not includesuction housings, etc. Conventional fibre disc sanding apparatuses areoperated without a back-up apparatus suitable for connection with asuction system. Further, the coarse nature of the abrasive material usedon conventional fibre discs, and the nature of the surfaces beinggrinded, makes fibre discs less likely than conventional, fine grainsand paper to become clogged with sanding debris.

Forming suction holes in conventional fibre discs can result inaccelerated wear on the forming tools (such as a press or die) due tothe nature of the strong abrasive materials coating the fibre disc.

The inventor has discovered that fibre discs can be used in combinationwith a back-up plate. The inventor has also discovered that fibre discscan be provided with suction holes, and can be used in combination witha suction system. Providing a fibre disc mounted to a back-up plate,and/or equipped with suction holes may help improve the performance ofthe fibre disc.

Referring to FIG. 26, a sanding apparatus 10100 includes a drivingapparatus 10102, a back-up apparatus 10104, a suction system 10152 andan abrasive sheet 10110. The driving apparatus 10102 can be any suitabledriving apparatus, including a rotatory driving apparatus (such as anair grinder and an electric grinder). The back-up apparatus 10104 isrotatably coupled to the driving apparatus 10102, and is rotatable abouta central axis 10154. The sanding apparatus 10100 may be generallysimilar to the sanding apparatuses 100, 1100, 2100, etc, and likeelements are identified using like reference numerals, starting at10100.

Referring also to FIG. 28, in this example, the back-up apparatus 10104includes a rigid back-up plate 10112 that is configured to be directlyconnected to the fibre disc abrasive sheet 10110. In this configuration,the back-up plate 10112 includes the abrasive mounting face 10108 andthe opposed rear face 10106. This back-up apparatus 10104 does notinclude a back-up pad. Alternatively, some type of compatible back-uppad, or other intermediate layer could be included between the back-upplate and the abrasive sheet.

The back-up plate 10112 includes a central mounting aperture 10246 thatis configured to accept a mounting fastener 10290, for example centralmounting nut 10290 a. The fibre disc abrasive sheet 10110 includes acorresponding central aperture 10248 that is registered with themounting aperture 10246. The mounting nut 10290 a extends through theapertures 10246, 10248 and secures the fibre disc abrasive sheet 10110to the back-up plate 10112. The mounting nut 10290 a can be any suitablefastener, including a conventional mounting nut that is conventionallyused to attached fibre discs to conventional driving apparatuses.

Optionally, the abrasive mounting face 10108 can include an adhesivelayer to help inhibit relative rotation between the fibre disc 10110 andthe back-up plate 10112 The adhesive layer can be any suitable type ofadhesive, including the two-layer, releasable adhesive described above.

The back-up plate 10112 can include plurality of plate suction apertures10178 extending through the back-up plate. In the illustrated example,the plate suction apertures 10178 are arranged along a constantcircumference, at a radial distance 10204 from the central axis 10154,toward the periphery of the back-up plate 10112. Alternatively, theapertures 10178 can be arranged in other suitable patterns, and need notbe on a constant circumference.

One example of an abrasive fibre disc 10110 that is suitable for usewith the back-up plate includes an abrasive surface coated 10146 withabrasive material and an opposed mounting surface 10296 adjacent the padattachment face 10108 of the back-up plate 10112. The fibre disc 10110also includes a plurality of disc suction holes 10184 registrable withcorresponding ones of the plurality of plate suction apertures 10178. Inthis configuration, the plurality of suction holes 10184 are spaced anequal radial distance from the central axis of rotation 10154.

A method of manufacturing abrasive fibre disc 10110 can include thesteps of i) providing a sheet of base material, ii) cutting the basematerial into a disc shape, iii) forming a central mounting aperture inthe centre of the disc, iv) forming a plurality of discrete suctionholes in the disc, and v) after forming the central mounting apertureand the plurality of suction apertures, coating at least one side of thedisc with abrasive material.

Optionally, the mounting aperture 102048 and the suction holes 10184 canbe formed generally simultaneously.

When manufactured using this method, the sidewalls 10298 of theplurality of suction holes 10184 can be coated with the abrasivematerial.

The sanding apparatus 10100 can also include a suction apparatus 10152in fluid communication with the plate suction apertures 10178 extractingsanding/grinding waste through the fiber disc 10110 and back-upapparatus 10104. The suction apparatus 10152 can be of any suitableconfiguration, and optionally can include a suction housing 10156 havinga suction housing inlet 10164 opposite the rear face 10106 of back-upplate 10112. The suction inlet 10164 is surrounded by a suction housingsidewall 10160. In this configuration, the plurality of plate suctionapertures 10178 are radially inboard from the suction housing sidewall10160.

The suction apparatus 10152 has a first edge 10162 that is adjacent butspaced apart from the rear face 10106 of the back-up plate 10112 by asuction spacing distance 10176. As described in detail above, thesuction spacing distance 10176 can be set to allow the back-up plate10112 to rotate relative to the suction housing sidewall 10160 whileconstricting airflow through the gap between the edge 10162 and theback-up plate 10112 to help preserve the suction.

Optionally, the suction spacing distance 10176 can be adjustable.Adjusting the suction space distance 10176 can adjust the size of thegap between the edge 10162 of the suction housing 10156 and the back-upplate 10112. Changing the size of the gap can vary the amount of airthat is drawn in through the gap, which may vary the amount of suctionat the abrasive mounting face 10108. For example, increasing the size ofthe gap, to suction spacing distance 10176 a shown in phantom (FIG. 30),may allow more air to be draw into the suction housing 10156, which maydecrease the suction at the abrasive mounting face 10108. Adjusting thesize of the gap in this manner may allow a user to adjust the amount ofsuction applied to the surface being grinded.

If the suction is too strong, the fibre disc 10110 may becomenon-rotatably stuck to the surface. This may inhibit grinding of thesurface. This may also cause damage to the driving apparatus.Alternatively, if the suction is too weak, grinding debris may not beeffectively drawn through the suction holes 10184 and plate suctionapertures 10178 for disposal. It may be desirable for a use to be ableto vary the level of suction while the grinding apparatus wherein thefirst edge 10162 is moveable relative to the back-up plate in adirection parallel to the central axis 10154 of rotation to alter thesuction spacing distance 10176 to adjust the suction strength.

In the present example, the suction apparatus 10152 includes a collar10300 that is movably coupled to the suction housing 10156. The collar10300 surrounds the suction housing sidewall 10160 and is translatablein the axial direction (i.e. toward and away from the back-up plate).Moving the collar 10300 translates the first edge 10162 relative to theback-up plate 10112. In the illustrated example, the collar 10300 is anannular ring of sheet metal that fits around, and can move axiallyrelative to the suction housing side wall 10160. Alternatively, thesuction apparatus need not include a separate movable collar. Instead,the suction housing 10156 can be movably connected to the drivingapparatus 10102 so that the entire suction housing 10156 can be moved tovary the suction spacing distance. A suitable securing apparatus, forexample a clamp or a securable actuator can be used to hold the suctionhousing 10156 in a desired position relative to the back-up plate.

A securing apparatus can be used to secure the ring 10300 to the suctionhousing 10156, to inhibit relative axial movement therebetween. In theillustrated example, the securing apparatus comprises an annular clamp10302 configured to clamp the collar 10300 against the housing sidewall10160. The position of the collar 10300 can then be adjusted byloosening the clamp 10302, sliding the collar 10300 into a desiredposition and then tightening the clamp 10302 to secure the collar 10300in place. Alternatively, other securing apparatuses can be used,including, for example, a threaded connection, a radial set screw, amovable actuator and an interference fit.

Optionally, the collar 10300 can be manually positioned by a user.Alternatively, the collar 10300 can be automatically movable, forexample using a suitable collar actuator (not illustrated), to maintaina desired level of suction at the abrasive mounting face 10108. In suchan example, the sanding apparatus 10100 can also include a variety ofsensors, transducers and controllers.

Optionally, the collar 10300 is movable while the back-up plate 10112 isrotating.

The size of the suction housing 10156, for example the diameter 10304 ofthe suction housing sidewall 10160 and the collar 10300, can be selectedbased on the size of the fibre disc 10110, and the location of the platesuction apertures 10178. The suction housing 10156 is selected so thatthe plate suction apertures 10178 are located radially inboard of thecollar 10300.

Configuration of an Auxiliary Member

In accordance with another aspect of this specification, which may beused by itself or with any one or more other aspects of thisspecification, an auxiliary member can be positioned between the back-uppad and the abrasive sheet. The auxiliary member can be permanently orremoveably attached to the back-up apparatus. Providing an auxiliarymember can allow a user to modify the properties of the back-upapparatus. One example of an auxiliary member is a sponge member that isgenerally softer and more compliant than the back-up pad to which it ismounted.

Referring to FIG. 29, optionally, a separate sponge member 11304 can beused in combination with the back-up pads described herein. The spongemember 1104 can be positioned between the back-up pad 11114 and theabrasive sheet 11110. The sponge member 1104 can be relatively softerand more pliable than the back-up pad 11114 material. Providing a spongemember 11304 may help facilitate gentler and/or more delicate sandingoperations, such as buffing and polishing, when used with acorresponding, appropriate abrasive material. The sponge member can bemade from any suitable material including, for example, sponge foams andsponge rubbers, and preferably is urethane foam.

The sponge member 11304 can be configured to include some of all of thefeatures of, or to be compatible with the back-up pads described above,including, for example, an adhesive interface layer 11124, and a varietyof suction apertures, channels and internal conduits (examples of whichare shown in phantom). The sponge member 11304 can also be configured sothat it can be engaged by a mounting tool, which may help align andmount the sponge member on a suitable back-up pad.

Optionally, the sponge member 11304 can be inserted between the back-uppad 11114 and a relatively rough abrasive sheet 11110. The outer face ofthe sponge member 11304 can also be coated with a relatively fineabrasive material. In this configuration a surface treating apparatuscan be quickly reconfigured from using a relative rough abrasivematerial to using a relatively fine abrasive material by removing theabrasive sheet 11110 to expose the outer surface of the sponge member11304.

A variety of examples of sanding apparatuses are described herein. Agiven sanding apparatus can include some, or all, or any combination orsub-combination of the features described herein. For example, a sandingapparatus can include an adhesive interface layer and a plurality ofsuction holes, and/or open suction channels and/or suction conduits.Similarly, a sanding apparatus can include a back-up pad formed from alive rubber material, be configured to use a central safety fastener andinclude a mechanical (hook and loop) interface layer. Any of theexamples herein can be configured to include the adhesive interfacelayer and/or the safety fastener.

Embodiments of sanding apparatuses may or may not include suctionsystems, depending on the application. If a suction system is desired,the sanding apparatus can be configured to include a plurality ofsuction apertures, channels and conduits as desired, and the abrasivesheets can be configured to include a corresponding plurality of suctionholes.

No example is intended to be limiting or exclusive of any other examplesdescribed herein, and a sanding apparatus can be equipped with anycompatible combination of features.

What has been described above has been intended to be illustrative ofthe invention and non-limiting and it will be understood by personsskilled in the art that other variants and modifications may be madewithout departing from the scope of the invention as defined in theclaims appended hereto.

1. A back-up apparatus for use with a surface treating apparatus, theback-up apparatus comprising: a) a back-up plate having a pad attachmentface; b) a back-up pad, the back-up pad having a first pad face, securedto the pad attachment face, and an opposed second pad face; c) an porousinterface layer, the interface layer comprising an inner face, securedto the second pad face, and an outer face; d) a layer of a firstadhesive provided on the outer face and extending into the interfacelayer; and e) a layer of a second adhesive provided on the layer of thefirst adhesive wherein the second adhesive is selected to releasablyadhesively bond to an abrasive sheet, and wherein the first and secondadhesives are selected such that the adhesive bond between the firstadhesive and the second adhesive is stronger than the adhesive bondbetween the second adhesive and the abrasive sheet whereby the layer ofsecond adhesive remains bonded to the layer of first adhesive when theabrasive sheet is separated from the back-up apparatus.
 2. The back-upapparatus of claim 1, wherein the back-up pad is resiliently flexibleand the interface layer is flexible whereby the back-up pad flexes tofollow the contours of a surface being sanded.
 3. The back-up apparatusof claim 1, wherein the interface layer is a pile material and the outerface comprises a plurality of engagement fibres extending away from theinterface layer.
 4. The back-up apparatus of claim 1, wherein the firstadhesive is mechanically worked into the interface layer and extendsbelow the outer face to provide a three dimensional adhesive layer. 5.The back-up apparatus of claim 1, wherein the interface layer coverssubstantially all of the outer face.
 6. The back-up apparatus of claim1, wherein the surface area of the interface layer is greater than thesurface area of the pad mounting face of the back-up plate.
 7. Theback-up apparatus of claim 1, wherein the back-up pad is a natural orsynthetic rubber.
 8. The back-up apparatus of claim 1, wherein the bondbetween the second adhesive and the abrasive sheet has a first bondstrength at 25° C. and a second bond strength at 400° C., the secondbond strength being at least 80% of the first bond strength.
 9. Theback-up apparatus of claim 1, wherein the back-up plate comprises aplurality of plate suction apertures fluidly connectable to a suctionhousing, the back-up pad comprises a plurality of pad suction aperturesin fluid communication with the plurality of plate suction apertures andthe interface layer comprises a plurality of interface suction aperturesin registration with the pad suction apertures.
 10. The back-upapparatus of claim 1, wherein the back-up plate comprises a plurality ofplate suction apertures fluidly connectable to a suction housing, theback-up pad comprises an open pad suction channel in fluid communicationwith the plurality of plate suction apertures and opening to the secondpad face and the interface layer comprises an interface suction openingregistered with the pad suction channel.
 11. A method of replacing anabrasive sheet on a back-up apparatus, the method comprising: f)providing a back-up apparatus comprising: i) a back-up plate having apad attachment face; ii) a back-up pad, the back-up pad having a firstpad face secured to the pad attachment face, and an opposed second padface; iii) a porous interface layer, the interface layer having an innerface secured to the second pad face, and an opposed outer face; iv) alayer of a first adhesive covering the outer face and coating aplurality of discrete fibres extending away from the abrasive mountingface; and v) a layer of a second adhesive provided on the first adhesiveand releasably adhesively bonded to the abrasive sheet; g) separatingthe abrasive sheet from the interface layer; h) providing a replacementabrasive sheet comprising a first side covered with abrasive materialand an opposed second side configured to releasably engage the layer ofsecond adhesive; i) aligning the second side of the replacement abrasivesheet with the abrasive mounting face of the interface layer; and j)pressing the second side of the replacement abrasive sheet against thelayer of second adhesive on the interface layer.
 12. The method of claim11, wherein the abrasive sheet comprises a base layer, the base layercomprising the first side covered with abrasive material, and comprisingan opposed rear face, and a film layer bonded to the opposed rear faceof the base layer, and the film layer comprising the opposed second sideconfigured to releasably engage the layer of second adhesive.
 13. Themethod of claim 11, wherein step b) is completed in the absence oftransferring the second adhesive from the abrasive mounting face to theabrasive sheet.
 14. The method of claim 11, further comprising sealingthe peripheral edges of the film layer to the abrasive mounting facewhereby debris is inhibited from being deposited between the abrasivemounting sheet and the film layer.
 15. The method of claim 11, whereinthe film layer is mylar.
 16. The method of claim 11, wherein the back-uppad is resiliently flexible and the interface layer is also flexiblewhereby the interface layer flexes with the back-up pad. 17-96.(canceled)